CN111511455B

CN111511455B - Honeycomb body and particle filter comprising a honeycomb body

Info

Publication number: CN111511455B
Application number: CN201880084303.2A
Authority: CN
Inventors: D·M·比尔; T·R·宝格; D·C·伯克宾德; T·J·克拉森; D·R·鲍尔斯; P·坦登; 王建国; 吴惠箐; 邢新峰
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2017-10-31
Filing date: 2018-10-31
Publication date: 2023-03-31
Anticipated expiration: 2038-10-31
Also published as: CN116078052A; US20200353401A1; CN111511455A; EP3694625A1; US11117124B2; US20210394168A1; US11504705B2; WO2019089806A1; MX2020004605A; US11458464B2; JP2021502897A; JP7187109B2; US20200254435A1

Abstract

The honeycomb body has a porous ceramic honeycomb structure having a first end, a second end, and a plurality of walls having wall surfaces defining a plurality of internal channels. A highly porous layer is disposed on one or more of the wall surfaces of the honeycomb body. The highly porous layer has a porosity greater than 90% and an average thickness greater than or equal to 0.5 μm and less than or equal to 10 μm. A method of manufacturing a honeycomb body includes depositing a layer precursor on a ceramic honeycomb body and bonding the layer precursor to the ceramic honeycomb body to form a highly porous layer.

Description

Honeycomb body and particle filter comprising a honeycomb body

Background

This application claims priority to U.S. provisional patent application serial No. 62/579,601, filed on 31, 10, 2017, and U.S. provisional patent application serial No. 62/725,978, filed on 31, 8, 2018, the contents of which are hereby incorporated by reference in their entirety.

Technical Field

The present description relates to honeycomb bodies, particulate filters comprising honeycomb bodies, and methods of making such honeycomb bodies and particulate filters.

Background

Ceramic wall-flow filters are used to remove particulates from a fluid exhaust stream (e.g., from an internal combustion engine exhaust). Examples include: a ceramic soot filter for removing particulates from diesel engine exhaust; and a Gasoline Particulate Filter (GPF) for removing particulates from gasoline engine exhaust. For a wall-flow filter, the exhaust gas to be filtered enters the inlet channels and exits the filter through the channel walls via the outlet channels, and as the gas traverses and exits the filter, particulates are trapped on or in the inlet channel walls. The particles may include soot and/or ash. After prolonged exposure to engine exhaust, ash and/or soot accumulation typically occurs within the filter.

Disclosure of Invention

Aspects of the present disclosure pertain to ceramic articles, such as honeycomb bodies and particulate filters, and methods of making and using the same. In some embodiments, the particulate filter comprises a honeycomb body comprising a porous ceramic honeycomb structure of porous walls comprising wall surfaces containing deposits of filter material defining a plurality of internal channels (channels). The porous walls comprise a porous bottom wall (base wall) and a deposit of filter material disposed on one or more of the porous bottom walls, wherein the porous walls form channels. The filter material deposit comprises one or more inorganic materials, such as one or more ceramic or refractory materials. The deposits of filter material are disposed on the walls to provide filtration efficiency enhancement of the honeycomb. In some embodiments, filtration efficiency is enhanced at least when the honeycomb is used from a clean state or from a regenerated state, such as when the honeycomb is not or substantially not accumulating ash or soot inside the honeycomb, such as when the honeycomb is new or has been regenerated to remove all or substantially all of the ash and/or soot. Significant accumulation of ash and/or soot inside the channels of the honeycomb body then typically occurs after prolonged exposure to engine exhaust gases (e.g., after prolonged use of the honeycomb body as a filter). In one or more embodiments, the filter material deposits are durable, e.g., have durability, e.g., withstand high gas or air flow through the particulate filter with little or no degradation in filtration performance.

In one or more embodiments, there is a deposit of filter material over substantially the entire surface, or even the entire surface, of one or more walls of the honeycomb. Thus, in some embodiments, the outer surface of the wall facing the channel, and thus defining the channel, comprises a deposit. In some embodiments, some surface portions of some walls are free of deposits, and thus some walls may include surface portions that are free of deposits. In some embodiments, a portion of the deposit of filter material is disposed in the porous bottom wall portion, for example, in the form of fingers or roots that extend partially into the bottom wall portion. In some embodiments, deposits of filter material are also present in the pores of the porous bottom wall, but do not penetrate the entire thickness of the bottom wall; thus, at least some of the inner portion of the bottom wall is free of any deposits. In some embodiments, there is a deposit at the surface of the walls as an integrated film or layer, and in some embodiments, an integrated continuous layer, such that at least some surfaces of the walls of the honeycomb comprise a film or layer; in some of these embodiments, the deposit is present on the entire surface of all the walls defining the channel or channels, for example those bottom walls which are completely or substantially completely covered by the deposit of filter material; in other of these embodiments, the deposit of filter material is present only on a portion of the surface of the bottom wall of the wall defining the one or more channels. The layer or membrane is porous, preferably highly porous, to allow gas to flow through the layer, and the bottom wall is also porous so that gas can flow through the porous wall. In some embodiments, there is a layer or film as a continuous coating on at least a portion of the surface or the entire surface of the one or more walls. In some preferred embodiments, only a portion of the cell walls of the honeycomb body of the particulate filter are provided with deposits of filter material, e.g., only corresponding to cells plugging the inlet flow channels of the honeycomb body.

In one aspect, the deposit of filter material comprises flame deposited filter material. In some embodiments, the porous walls of the honeycomb structure comprise deposits present as an integrated layer or film that make up at least a portion of the surface of the walls of one or more channels, and in some of these embodiments, at least a portion of the surface or the entire surface of one or more walls comprises a continuous layer.

In some embodiments, the surface of one or more walls of the honeycomb structure comprises a plurality of discrete regions of deposits of filter material.

In some embodiments, the filter material deposit partially blocks a portion of some of the pores of the porous bottom wall while still allowing gas flow through the wall.

In one set of embodiments disclosed herein, a honeycomb body comprises a honeycomb structure comprising: a first end, a second end, and a plurality of walls extending from the first end to the second end. The plurality of walls includes a plurality of porous walls. The porous wall includes a porous bottom wall. At least some of the porous wall surfaces further comprise a deposit of filter material. The plurality of walls define a plurality of channels extending from the first end to the second end. Some of the channels are plugged at or near the first end, and some of the remaining channels are plugged at or near the second end, thereby providing a wall-flow filter flow path that constitutes the following gas flow: enters the inlet channel from the first end, passes through a portion of the porous wall, and exits through the outlet channel and exits the second end. In some embodiments, the filter material deposit is present on a wall defining one or more of the inlet channels; in some of these embodiments, the deposits of filter material are not present on the walls defining the outlet channels.

In some embodiments, the deposit of filter material is in the form of a thin highly porous layer. In some embodiments, the porous walls comprise a porous inorganic layer having a porosity greater than 90% and an average thickness greater than or equal to 0.5 μm and less than or equal to 10 μm.

In another aspect, a method of making a honeycomb body comprises: depositing a filter material with a gaseous carrier fluid onto the bottom wall of the ceramic honeycomb body by flowing the filter material toward the ceramic honeycomb body; and bonding the filter material to the porous bottom wall of the ceramic honeycomb body. In particular embodiments, the filter material deposit is bonded by thermal sintering or fusing with the bottom wall portion or a previously deposited filter material. For example, the deposit forms a porous inorganic layer having a porosity greater than 90% and an average thickness greater than or equal to 0.5 μm to less than or equal to 10 μm.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments described herein and together with the description serve to explain the principles and operations of the claimed subject matter.

Drawings

FIG. 1 schematically illustrates a honeycomb body according to embodiments disclosed and described herein;

FIG. 2 schematically illustrates a honeycomb body having a soot load in accordance with embodiments disclosed and described herein;

3A, 3B, 3C, and 3D are Scanning Electron Microscope (SEM) images of amorphous phase decomposition evaporation layer precursors deposited onto honeycomb bodies according to embodiments disclosed and described herein;

4A, 4B, 4C, and 4D are Transmission Electron Microscope (TEM) images of amorphous phase decomposition evaporation layer precursors deposited onto honeycomb bodies at different layer precursor flow rates according to embodiments disclosed and described herein;

FIGS. 5A, 5B, 5C, and 5D are Scanning Electron Microscope (SEM) images of a crystalline phase coating deposited onto a honeycomb body according to embodiments disclosed and described herein;

FIG. 6 is a graphical representation of the filtration efficiency of a honeycomb body according to embodiments disclosed and described herein;

FIG. 7A is a graphical representation of backpressure versus flow rate for a honeycomb body in accordance with embodiments disclosed and described herein;

FIG. 7B is a graphical representation of backpressure versus soot load for a honeycomb body in accordance with embodiments disclosed and described herein;

fig. 8A and 8B are SEM photographs of a honeycomb body according to embodiments disclosed and described herein;

FIG. 9 is a graphical representation of the filtration efficiency of a honeycomb body according to embodiments disclosed and described herein;

FIG. 10A is a graphical representation of backpressure versus flow rate for a honeycomb body in accordance with embodiments disclosed and described herein;

FIG. 10B is a graphical representation of backpressure versus soot load for a honeycomb body in accordance with embodiments disclosed and described herein;

11A and 11B are SEM photographs of a honeycomb body according to embodiments disclosed and described herein;

FIG. 12 is an XRD analysis of an amorphous phase decomposition layer precursor (as-deposited prior to sintering) and a crystalline phase ceramic layer (after sintering);

13A and 13B are scanning electron microscope images at different magnifications of amorphous phase decomposition layer precursors deposited onto honeycomb bodies in accordance with embodiments disclosed and described herein;

13C and 13D are scanning electron microscope images at different magnifications of a crystalline ceramic layer deposited onto a honeycomb body in accordance with embodiments disclosed and described herein;

figure 14 shows XRD scans of decomposed layer precursors in as-deposited state, after exposure to 850 ℃ for 6 hours, after exposure to 850 ℃ for 12 hours, and after exposure to 1150 ℃ sintering for 0.5 hours;

FIG. 15 is a graphical representation of the filtration efficiency of a honeycomb body according to embodiments disclosed and described herein;

FIG. 16A is a graphical representation of backpressure versus flow rate for a honeycomb body in accordance with embodiments disclosed and described herein;

FIG. 16B is a graphical representation of backpressure versus soot load for a honeycomb body in accordance with embodiments disclosed and described herein;

FIG. 17 schematically illustrates a particulate filter according to embodiments disclosed and described herein;

FIG. 18 is a cross-sectional view of the particulate filter of FIG. 17;

FIG. 19 is a flow diagram of a flame pyrolysis process according to an embodiment;

FIG. 20 schematically shows an experimental apparatus for testing a particulate filter according to one or more embodiments;

FIG. 21 is a graph of filtration efficiency versus time (in seconds) for two examples made according to an embodiment of the present disclosure as compared to a comparative example;

FIG. 22 is a graph of filtration efficiency versus soot load (g/L) for two examples made according to an embodiment of the present disclosure compared to a comparative example;

FIG. 23 is a view according to the disclosureThe two examples made in accordance with the open content of the embodiment have a pressure drop and a volume flow (m) in comparison with the comparative example ³ A graph of relationships,/h);

FIG. 24 is laboratory filtration efficiency/filtration area (%/m) ² ) Plot against laboratory pressure drop (in kPa); and

figure 25 shows a plot of parameter NPV versus parameter NMFV for samples prepared according to an embodiment of the present disclosure.

Detailed Description

Reference will now be made in detail to embodiments of honeycomb bodies including porous honeycomb bodies having highly porous layers thereon, which embodiments are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In an embodiment, the honeycomb body comprises a porous ceramic honeycomb body comprising: a first end, a second end, and a plurality of walls having wall surfaces defining a plurality of internal passages. A porous inorganic layer is disposed on one or more of the wall surfaces of the honeycomb body. The inorganic layer has a porosity of greater than 90%, and the inorganic layer has an average thickness greater than or equal to 0.5 μm and less than or equal to 10 μm. Various embodiments of honeycomb bodies and methods of making such honeycomb bodies are described herein with particular reference to the drawings. In some embodiments, a particulate filter is provided, the particulate filter comprising a honeycomb body comprising a plugged porous ceramic honeycomb structure comprising a plurality of intersecting porous walls comprising porous wall surfaces defining a plurality of channels extending from an inlet end to an outlet end of the structure, the plurality of channels comprising inlet channels sealed at or near the outlet end and having a surface area and outlet channels sealed at or near the inlet end and having a surface area, the inlet and outlet channels defining a filtration zone, wherein one or more of the porous wall surfaces defining the inlet channels comprises a bottom wall portion and a deposit of filter material disposed on the bottom wall portion, wherein the deposit of filter material is disposed on the bottom wall portion, and wherein, at room temperature, upon exposure to 850Nm, the deposit of filter material is at room temperature ³ The particulate filter exhibits a change in filtration efficiency of less than 5% after a high flow condition of air for 1 minute, and wherein the change in filtration efficiency is determined by measuring the difference between the number of soot particles introduced into the particulate filter and the number of soot particles leaving the particulate filter before and after exposure to the high flow condition, wherein the soot particles have a median particle size of 300Nm at 51Nm ³ The soot particle concentration in the air stream flowing through the particle filter at a flow rate of/h, room temperature and a velocity of 1.7m/s was 500,000 particles/cm ³ This is measured by a particle counter (e.g., using a Lighthouse hand held (Lighthouse hand held) 3016.1 cfm particle counter, available from Lighthouse global Solutions, inc (Lighthouse world Solutions), 30 seconds upstream of the particle filter, and 30 seconds downstream of the particle filter). In some embodiments, the method further comprises exposing the composition to 850Nm at room temperature ³ After 1 minute of high flow condition of/h air, the particulate filter exhibits a filtration efficiency change of less than 20%, 15%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, or even less than 1%.

In some embodiments, the filter material deposits are preferably mechanically stable, e.g., resistant to movement or rearrangement, e.g., due to high gas flow through a plugged honeycomb structure of the particulate filter and/or due to mechanical vibration. In one or more embodiments, the filter material deposits are stable when exposed to water, such that the deposits maintain their orientation or position on the cell walls. In other words, according to some embodiments, the filter material deposit is bonded to the porous ceramic bottom wall. In some embodiments, the deposits are chemically bonded, not merely by physical bonding. For example, in some embodiments, the flame pyrolysis filter material deposits are fused or sintered to the porous ceramic bottom wall. Further, in some embodiments, the deposits of flame pyrolyzed filter material are fused or sintered to one another to form a layer of porous inorganic material.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include embodiments having plural referents, unless the context clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the context clearly dictates otherwise.

As used herein, "having," including, "" comprising, "" contains, "or" containing "and the like are used in their open-ended form and generally mean" including, but not limited to.

As used herein, a honeycomb body is a shaped ceramic honeycomb structure of intersecting walls that form cells to define channels. The ceramic honeycomb structure may be formed, extruded or molded, and may be of any shape or size. For example, the ceramic honeycomb structure may be formed from cordierite or other suitable ceramic materials.

As used herein, a honeycomb body may also be defined as a shaped ceramic honeycomb structure having at least one layer applied to a wall surface of the honeycomb structure and configured to filter particulate matter from a gas stream. More than one layer may be applied at the same location on the honeycomb. The layers may be inorganic or organic, or both. For example, in one or more embodiments, the honeycomb may be formed from cordierite or other ceramic materials and may have a high porosity layer applied to the surface of the cordierite honeycomb structure. The layers may be "filter materials" that are used to provide enhanced filtration efficiency, both locally through the walls and at the walls and globally through the honeycomb. The filter material is not considered catalytically active because it does not react with the components of the gaseous mixture of the exhaust stream.

As used herein, "green" or "green ceramic" are used interchangeably and refer to unsintered material unless otherwise specified.

The honeycomb of one or more embodiments may include a honeycomb structure and a layer disposed on one or more walls of the honeycomb structure. In some embodiments, the layer is applied to the surface of a wall present in the honeycomb structure where the wall has a surface defining a plurality of internal channels. When present, the internal channels may have various cross-sectional shapes, such as circular, oval, triangular, square, pentagonal, hexagonal, or tessellated, or any combination of these, and may be arranged in any suitable geometric configuration. When present, the internal channels can be discrete or intersecting, and can extend through the honeycomb body from a first end thereof to a second end opposite the first end.

Referring now to FIG. 1, a honeycomb body 100 according to one or more embodiments shown and described herein is shown. In an embodiment, the honeycomb body 100 includes a plurality of walls 115 defining a plurality of internal channels 110. The plurality of internal channels 110 and cross channel walls 115 extend between the first end 105 and the second end 135 of the honeycomb body.

In one or more embodiments, the honeycomb body may be formed from cordierite, aluminum titanate, enstatite, mullite, forsterite, corundum (SiC), spinel, sapphire, and periclase. Generally, cordierite is a compound having a formula (Mg, fe) ₂ Al ₃ (Si ₅ AlO ₁₈ ) A solid solution of the composition (1). In some embodiments, by varying the particle size of the ceramic raw material, the pore size of the ceramic material may be controlled, the porosity of the ceramic material may be controlled, and the particle size distribution of the ceramic material may be controlled. In addition, pore formers may be included in the ceramic batch materials used to form the honeycomb bodies.

In some embodiments, the average thickness of the walls of the honeycomb body can be greater than or equal to 25 μm to less than or equal to 250 μm, for example: greater than or equal to 45 μm to less than or equal to 230 μm, greater than or equal to 65 μm to less than or equal to 210 μm, greater than or equal to 65 μm to less than or equal to 190 μm, or greater than or equal to 85 μm to less than or equal to 170 μm. The walls of the honeycomb body can be described as having: comprising a bottom wall portion of a body portion (also referred to herein as the body), and a surface portion (also referred to herein as the surface). The surface portion of the walls extends into the walls from the surface of the walls of the honeycomb body toward the body portion of the honeycomb body. The surface portion may extend from 0 (zero) into the bottom wall portion of the walls of the honeycomb body to a depth of about 10 μm. In some embodiments, the surface portion may extend about 5 μm, about 7 μm, or about 9 μm (i.e., 0 (zero) depth) into the bottom wall portion of the wall. The body portion of the honeycomb body constitutes the wall minus the thickness of the surface portion. Thus, the body portion of the honeycomb body can be determined by the following equation:

t _{general assembly} -2t _{Surface of}

In the formula, t _{General assembly} Is the total thickness of the wall, and t _{Surface of} Is the thickness of the wall surface.

In one or more embodiments, the body of the honeycomb has a body mean pore size (bulk mean pore size) of greater than or equal to 7 μm to less than or equal to 25 μm, for example: greater than or equal to 12 μm to less than or equal to 22 μm or greater than or equal to 12 μm to less than or equal to 18 μm. For example, in some embodiments, the bulk average pore size of the body of the honeycomb body can be about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, about 19 μm, or about 20 μm. In general, there is a statistical distribution of pore sizes for any given material. Thus, the term "median pore diameter" or "D50" refers to the situation where 50% of the pores are located at and below it, and the remaining 50% are located at it, based on the statistical distribution of all pores. The pores may be fabricated in the ceramic body by at least one of: (1) inorganic batch material particle size and size distribution; (2) furnace/thermal treatment firing time and temperature schedule; (3) Furnace atmosphere (e.g., low or high oxygen content and/or water content); and (4) pore formers such as: polymers and polymer particles, starch, wood flour, hollow inorganic particles, and/or graphite/carbon particles.

In some embodiments, the bulk porosity of the body of the honeycomb without regard to the coating can be greater than or equal to 50% to less than or equal to 70%, as measured by mercury intrusion. Methods of measuring surface porosity include Scanning Electron Microscopy (SEM), which is particularly useful for measuring surface porosity and bulk porosity independently of one another. In one or more embodiments, the bulk porosity of the honeycomb can be, for example, less than 70%, less than 65%, 60%, less than 58%, less than 56%, less than 54%, or less than 52%.

In one or more embodiments, the surface median pore diameter of the surface portions of the honeycomb body is greater than or equal to 7 μm to less than or equal to 20 μm, for example: greater than or equal to 8 μm to less than or equal to 15 μm or greater than or equal to 10 μm to less than or equal to 14 μm. For example, in some embodiments, the median pore diameter at the surface of the honeycomb body can be about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, or about 15 μm.

In some embodiments, the surface porosity of the surface of the honeycomb body prior to application of the layer can be greater than or equal to 35% to less than or equal to 50%, as measured by SEM. In one or more embodiments, the surface porosity of the honeycomb may be less than 65%, for example: less than 60%, less than 55%, less than 50%, less than 48%, less than 46%, less than 44%, less than 42%, less than 40%, less than 48%, or less than 36%.

Referring now to fig. 17 and 18, a honeycomb body in the form of a particulate filter 300 is schematically shown. The particulate filter 300 may be used as a wall-flow filter to filter particulate matter from an exhaust stream 350 (e.g., an exhaust stream emitted from a gasoline engine, in which case the particulate filter 300 is a gasoline particulate filter). The particulate filter 300 generally includes a honeycomb body having a plurality of channels 301 or cells extending between an inlet end 302 and an outlet end 404 defining an overall length L _a . The channels 301 of the particulate filter 300 are formed and at least partially defined by a plurality of cross channel walls 306 extending from an inlet end 302 to an outlet end 304. The particulate filter 300 may further comprise a skin layer 305 surrounding the plurality of channels 301. The skin may be extruded to form such a skin layer 305 during the formation of the channel walls 306, or may be formed in a later process as an after-applied skin layer, such as by applying a skin adhesive to the outer peripheral portions of the channel.

Shown in fig. 18 is an axial cross-section of the particulate filter 300 of fig. 17. In some embodiments, certain channels are designated as ingress channels 308 and certain other channels are designated as egress channels 310. In some embodiments of particulate filter 300, at least a first set of channels may be plugged by plugs 312. Generally, the plugs 312 are disposed near the ends (i.e., inlet or outlet ends) of the channels 301. The plugs are typically arranged in a predetermined pattern, such as a checkerboard pattern as shown in FIG. 17, with each other channel plugged at the ends. The inlet channels 308 may be plugged at or near the outlet end 304, and the outlet channels 310 may be plugged at or near the inlet end 302 on channels that do not correspond to inlet channels, as shown in FIG. 3. Thus, each cell may be plugged only at or near one end of the particulate filter.

While fig. 17 generally shows a checkerboard plugging pattern, it is to be understood that alternative plugging patterns may be selected in the porous ceramic honeycomb article. In the embodiments described herein, the particulate filter 300 may be formed to have a channel density of up to about 600 channels per square inch (cpsi). For example, in some embodiments, the particulate filter 100 may have a channel density of about 100cpsi to about 600 cpsi. In some other embodiments, the particulate filter 100 may have a channel density of about 100cpsi to about 400cpsi, or even about 200cpsi to about 300 cpsi.

In the embodiments described herein, the channel walls 306 of the particulate filter 300 may have a thickness greater than about 4 mils (101.6 microns). For example, in some embodiments, the thickness of the channel walls 306 may be about 4 mils up to about 30 mils (762 micrometers). In some other embodiments, the thickness of channel walls 306 may be about 7 mils (177.8 microns) to about 20 mils (508 microns).

In various embodiments, the honeycomb body is configured to filter particulate matter from a gas stream. Thus, the median pore size, porosity, geometry, and other design aspects of both the body and surface of the honeycomb are selected to take into account these filtration requirements of the honeycomb. For example, as shown in the embodiment of fig. 2, the walls 210 of the honeycomb body 200 have a layer 220 disposed thereon, preferably by heat treatment sintering or any other means of bonding. The layer 220 can include particles 225 that deposit on the walls 210 of the honeycomb body 200 and help prevent particulate matter from exiting the honeycomb body (e.g., soot and ash) with the gas stream 230 and from plugging bottom wall portions of the walls 210 of the honeycomb body 200. In this manner, according to embodiments, layers 220 may serve as the primary filtration component, while the bottom wall portion of the honeycomb body may be configured to minimize pressure drop in any other manner, such as compared to a conventional honeycomb body without such layers. As used herein, pressure drop is measured using a differential pressure sensor that measures the pressure drop over the axial length of the filter. Since the pore size of the layer 220 is smaller than the bottom wall portion, the layer will filter a majority of the smaller sized particulate matter, but it is contemplated that the bottom wall portion of the walls of the honeycomb filter will be effective for filtering some of the larger sized particulate matter. As described in more detail herein, the honeycomb body can be formed by a suitable method, such as a flame deposition method, which achieves the formation of a highly porous thin layer on at least some surfaces of the walls of the honeycomb body.

In one or more embodiments, the porosity of the layers disposed on the walls of the honeycomb body as measured by SEM is greater than or equal to 80%, such as greater than 90%. In other embodiments, the porosity of the layers disposed on the walls of the honeycomb body is greater than or equal to 92%, such as greater than or equal to 93% or greater than or equal to 94%. In other embodiments, the porosity of the layers disposed on the walls of the honeycomb body is greater than or equal to 95%, such as greater than or equal to 96% or greater than or equal to 97%. In various embodiments, the porosity of the layers disposed on the walls of the honeycomb body is less than or equal to 99%, such as less than or equal to 97%, less than or equal to 95%, less than or equal to 94%, or less than or equal to 93%. The high porosity of the layers on the walls of the honeycomb enables the layers to be applied to the honeycomb without significantly affecting the pressure drop of the honeycomb as compared to the pressure drop of an identical honeycomb that does not contain a layer thereon. SEM and X-ray tomography are used to measure surface and bulk porosity independently of each other. Obtaining porosity by density calculation, comprising: the weight of the inorganic layer and its thickness were measured to obtain the layer density, and the porosity of the layer was calculated according to the equation layer porosity = 1-layer density/inorganic material density. For example, for a layer comprising mullite, the "inorganic material density" is the density of the mullite.

As noted above, the layers on the walls of the honeycomb are very thin relative to the thickness of the bottom wall portions of the walls of the honeycomb, and the layers also have very high porosity and permeability. As discussed in more detail below, layers can be formed on a honeycomb body by methods that enable the layers to be applied to the surfaces of the walls of the honeycomb body in very thin layers. In embodiments, the average thickness of the layers on the bottom wall portions of the walls of the honeycomb body is greater than or equal to 0.5 μm to less than or equal to 30 μm, such as greater than or equal to 0.5 μm to less than or equal to 20 μm, greater than or equal to 0.5 μm to less than or equal to 10 μm, such as greater than or equal to 0.5 μm to less than or equal to 5 μm, greater than or equal to 1 μm to less than or equal to 4.5 μm, greater than or equal to 1.5 μm to less than or equal to 4 μm, or greater than or equal to 2 μm to less than or equal to 3.5 μm.

As discussed above, the layers can be applied to the walls of the honeycomb by methods that enable the inorganic layers to have a small median pore size. This small median pore size enables the layer to filter out a high percentage of particles and prevents the particles from penetrating the honeycomb and depositing into the pores of the honeycomb as described above with respect to fig. 2. The small median pore size of the layers according to embodiments increases the filtration efficiency of the honeycomb body. In one or more embodiments, the median pore diameter of the layers on the walls of the honeycomb is greater than or equal to 0.1 μm to less than or equal to 5 μm, for example: greater than or equal to 0.5 μm to less than or equal to 4 μm or greater than or equal to 0.6 μm to less than or equal to 3 μm. For example, in some embodiments, the median pore diameter of the layers on the walls of the honeycomb body can be about 0.5 μm, about 0.6 μm, about 0.7 μm, about 0.8 μm, about 0.9 μm, about 1 μm, about 2 μm, about 3 μm, or about 4 μm.

While in some embodiments, the layers on the walls of the honeycomb body may cover substantially 100% of the wall surfaces defining the internal channels of the honeycomb body, in other embodiments, the layers on the walls of the honeycomb body cover less than substantially 100% of the wall surfaces defining the internal channels of the honeycomb body. For example, in one or more embodiments, the layer on the walls of the honeycomb body covers at least 70% of the wall surfaces defining the internal channels of the honeycomb body, at least 75% of the wall surfaces defining the internal channels of the honeycomb body, at least 80% of the wall surfaces defining the internal channels of the honeycomb body, at least 85% of the wall surfaces defining the internal channels of the honeycomb body, at least 90% of the wall surfaces defining the internal channels of the honeycomb body, or at least 85% of the wall surfaces defining the internal channels of the honeycomb body.

The honeycomb body can have a first end and a second end as described above with reference to fig. 1. The first end and the second end are spaced apart by an axial length. In some embodiments, the layers on the walls of the honeycomb body can extend the entire axial length of the honeycomb body (i.e., extend along 100% of the axial length). However, in other embodiments, the layers on the walls of the honeycomb body extend along at least 60% of the axial length, for example: extend along at least 65% of the axial length, extend along at least 70% of the axial length, extend along at least 75% of the axial length, extend along at least 80% of the axial length, extend along at least 85% of the axial length, extend along at least 90% of the axial length, or extend along at least 95% of the axial length.

In an embodiment, the layers on the walls of the honeycomb body extend from a first end of the honeycomb body to a second end of the honeycomb body. In some embodiments, the layers on the walls of the honeycomb body extend the entire distance from the first surface of the honeycomb body to the second surface of the honeycomb body (i.e., along 100% of the distance from the first surface of the honeycomb body to the second surface of the honeycomb body). However, in one or more embodiments, the layers on the walls of the honeycomb body extend along 60% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, such as along 65% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, along 70% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, along 75% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, along 80% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, along 85% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, along 90% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body, or along 95% of the distance between the first surface of the honeycomb body and the second surface of the honeycomb body.

In one or more embodiments, the layers on the walls of the honeycomb body are disposed as a continuous coating on the wall surfaces. As used herein, a "continuous coating" is a region in which no portion of the region is substantially free of bare or free of layer material. In one or more embodiments, at least 50% of the layers are disposed as continuous layers on the wall surfaces of the honeycomb body, for example: at least 60% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, at least 70% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, at least 80% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, at least 90% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, at least 92% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, at least 94% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, at least 96% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body, or at least 98% of the layers are arranged as continuous layers on the wall surfaces of the honeycomb body. In other embodiments, 100% of the layers are disposed as continuous layers on the wall surfaces of the honeycomb body.

As noted above, and without being bound to any particular theory, it is believed that the reason for achieving low pressure drop with the honeycomb of embodiments is because the layers on the honeycomb are the primary filtration components of the honeycomb, which enables more flexible honeycomb designs. The selection of a honeycomb body with a low pressure drop in accordance with embodiments in combination with a low thickness and high porosity layer on the honeycomb body achieves a lower pressure drop for the embodiment honeycomb body compared to conventional honeycomb bodies. In embodiments, the layers on the honeycomb are 0.1 to 30g/L. In an embodiment, the layers present may be: 0.2 to 20g/L, 0.3 to 25g/L, 0.4 to 20g/L, 1 to 10g/L. In some embodiments, the pressure drop across the honeycomb (i.e., clean pressure drop without soot or ash) is less than or equal to 10%, such as less than or equal to 9% or less than or equal to 8%, as compared to a honeycomb without the thin, high porosity inorganic layer. In other embodiments, the pressure drop across the honeycomb body is less than or equal to 7%, such as less than or equal to 6%. In other embodiments, the pressure drop across the honeycomb body is less than or equal to 5%, such as less than or equal to 4% or less than or equal to 3%.

As noted above, and without being bound to any particular theory, the small cell size in the layers on the walls of the honeycomb achieves a honeycomb with good filtration efficiency even before ash or soot accumulation occurs in the honeycomb. The filtration efficiency of the honeycombs was measured using the protocol proposed by Tandon et al (65 chemical engineering science 4751-60 (2010)). As used herein, the initial filtration efficiency of a honeycomb body refers to a honeycomb body (e.g., a new or regenerated honeycomb body) in a clean state that does not contain any measurable soot or ash loading. In embodiments, the initial filtration efficiency (i.e., clean filtration efficiency) of the honeycomb body is greater than or equal to 70%, such as greater than or equal to 80% or greater than or equal to 85%. In other embodiments, the initial filtration efficiency of the honeycomb is greater than 90%, such as greater than or equal to 93%, or greater than or equal to 95%, or greater than or equal to 98%.

According to embodiments, the layers on the walls of the honeycomb are thin and have high porosity, and in some embodiments, the layers on the walls of the honeycomb also have good chemical durability and physical stability. Particularly if the layers are consolidated, sintered, or otherwise bonded to the surface of the honeycomb after the layer materials are applied to the walls of the honeycomb, as discussed in more detail below. In embodiments, the chemical durability and physical stability of the layers on the honeycomb can be determined by: the honeycomb bodies were subjected to test cycles including burn-out cycles and aging tests, and the initial filtration efficiencies were measured before and after the test cycles. For example, one exemplary method of measuring the chemical durability and physical stability of a honeycomb body comprises: measuring the initial filtration efficiency of the honeycomb body; loading soot onto the honeycomb body under simulated operating conditions; burning off the accumulated soot at a temperature of about 650 ℃; subjecting the honeycomb to an aging test at 1050 ℃ and 10% humidity for 12 hours; and measuring the filtration efficiency of the honeycomb body. Multiple cycles of soot accumulation and burn-out may be performed. The small filtration efficiency change (Δ FE) before and after the test cycle indicates better chemical durability and physical stability of the layer on the honeycomb. In some embodiments, Δ FE is less than or equal to 5%, e.g., less than or equal to 4% or less than or equal to 3%. In other embodiments, Δ FE is less than or equal to 2% or less than or equal to 1%.

In some embodiments, the layers on the walls of the honeycomb body may comprise one or a mixture of the following ceramic components, for example, selected from the group consisting of: siO 2 ₂ 、Al ₂ O ₃ 、MgO、ZrO ₂ 、CaO、TiO ₂ 、CeO ₂ 、Na ₂ O, pt, pd, ag, cu, fe, ni, and mixtures thereof. Thus, the layers on the walls of the honeycomb body may comprise oxide ceramics or aluminum silicates. As described in more detail below, methods of fabricating layers on honeycomb bodies according to embodiments may enable tailoring of layer compositions for a given application. This may be advantageous because the ceramic components may be combined to match, for example, physical properties of the honeycomb body, such as Coefficient of Thermal Expansion (CTE) and young's modulus, which may improve the physical stability of the honeycomb body. In some embodiments, the layers on the walls of the honeycomb body may include cordierite, aluminum titanate, enstatite, mullite, forsterite, corundum (SiC), spinel, sapphire, and periclase. In some embodiments, cordierite, aluminum titanate, enstatite, mullite, forsterite, corundum (SiC), spinel, sapphire, and/or periclase are synthetic. In one or more embodiments, the inorganic layer comprises synthetic mullite. Mullite is a rare silicate mineral and is based on the general structure xAl ₂ O ₃ ·ySiO ₂ Two stoichiometric forms can be formed, 3Al ₂ O ₃ ·2SiO ₂ Or 2Al ₂ O ₃ ·SiO ₂ . The preparation of the synthesized mullite comprises the steps of controlling the process to have the target x/y of 1.5-2 or controlling the target Al/Si mass ratio of 2.9-3.8.

In some embodiments, the composition of the layers on the walls of the honeycomb body is the same as the composition of the honeycomb body. However, in other embodiments, the composition of the layers is different from the composition of the honeycomb body.

According to one or more embodiments, the permeability of the layer is ≧ 10 ^-15 m ² . In some embodiments, the permeability of the layer is ≧ 10 ^-14 m ² E.g.. Gtoreq.10 ^-13 m ² Or not less than 10 ^-12 m ² 。

In some embodiments, the layer comprises mullite and has an average particle size of greater than or equal to 5nm to less than or equal to 3 μm. In such embodiments, the thickness and porosity of the layers may be thicknesses that depend on the desired properties of the honeycomb.

In some embodiments, the layer comprises alumina and has an average particle size of greater than or equal to 10nm to less than or equal to 3 μm. In some embodiments, the average particle size is greater than or equal to 100nm to less than or equal to 3 μm, such as greater than or equal to 500nm to less than or equal to 3 μm, or greater than or equal to 500 μm to less than or equal to 2 μm. In such embodiments, the thickness and porosity of the layers on the honeycomb body can be a thickness that depends on the desired properties of the honeycomb body.

The properties of the layers, and thus the honeycomb as a whole, have an effect on the ability to apply a thin layer of high porosity having a small median pore diameter to the honeycomb.

According to some embodiments disclosed and described herein, a method of making a honeycomb body comprises: atomizing, vaporizing or thin atomizing the layer precursor such that the layer precursor can be carried by the gaseous carrier fluid; depositing the atomized, vaporized or thin-atomized layer precursor onto a ceramic honeycomb structure; and bonding the atomized, vaporized or thinly atomized layer precursor to the ceramic honeycomb structure to form a layer on the ceramic honeycomb structure. In embodiments, the gaseous carrier fluid may be, for example, air, oxygen, or nitrogen. In some embodiments, the layer precursor may be combined with a solvent, such as a solvent selected from the group consisting of: methoxyethanol, ethanol, water, and mixtures thereof. In one or more embodiments, the layer precursor is blown into the internal channels of the ceramic honeycomb structure. The layer precursor particles can be bonded to the ceramic honeycomb structure by any suitable method, including applying moisture, e.g., steam or humidity, heat, or radiation, e.g., microwaves, to the layer precursor after the layer precursor is deposited onto the ceramic honeycomb structure.

According to some embodiments disclosed and described herein, a method of making a honeycomb body comprises: flame pyrolysis deposition of layers is provided to ceramic honeycomb structures, which provides for the deposition of very thin layers with high porosity and small median pore size. In an embodiment, a method of making a honeycomb body comprises: vaporizing the layer precursor by contacting the layer precursor with a vaporizing gas to form a vaporized layer precursor (the layer precursor may comprise a precursor material and a solvent); decomposing the vaporized layer precursor by contacting the vaporized layer precursor with a flame; depositing the vaporized layer precursor onto a ceramic honeycomb structure; and sintering the vaporized layer precursor to form the honeycomb body, wherein the honeycomb body comprises a layer coating the walls of at least a portion of the ceramic honeycomb structure. In one or more embodiments, the layer precursor is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

In some embodiments, a method of forming a honeycomb body includes forming or obtaining a layer precursor including a ceramic precursor material and a solvent. The ceramic precursor materials of the layer precursors include conventional raw ceramic materials as, for example: siO 2 ₂ 、Al ₂ O ₃ 、TiO ₂ 、MgO、ZrO ₂ 、CaO、CeO ₂ 、Na ₂ Sources of O, pt, pd, ag, cu, fe, ni, and the like. For example, in some embodiments, the ceramic precursor material is selected from the group consisting of: tetraethyl orthosilicate, magnesium ethoxide and aluminum (III) tri-sec-butoxide, trimethylaluminum, alCl ₃ 、SiCl ₄ 、Al(NO ₃ ) ₃ Aluminum isopropoxide, octamethylcyclotetrasiloxane, and mixtures thereof. By usingThe solvent in the layer precursor is not particularly limited as long as it can maintain the ceramic precursor material suspended in the solvent, and the solvent can be vaporized at a temperature of less than 200 ℃. In embodiments, the solvent is selected from the group consisting of: methoxyethanol, ethanol, water, xylene, methanol, ethyl acetate, benzene, and mixtures thereof.

In some embodiments, the layer precursor is vaporized by contacting the layer precursor with a vaporizing fluid to form a vaporized layer precursor. In one or more embodiments, the vaporizing fluid is selected from the group consisting of: oxygen (O) ₂ ) Water (steam, H) ₂ O), nitrogen (N) ₂ ) And mixtures thereof. The vaporizing fluid flows at a high flow rate relative to the flow rate of the layer precursor, such that when the vaporizing fluid contacts the layer precursor, the layer precursor is vaporized to the molecular level by the vaporizing fluid. For example, in an embodiment, the vaporized fluid is a gas flowing at a flow rate of: greater than or equal to 3L/min to less than or equal to 100L/min, such as greater than or equal to 4L/min to less than or equal to 6.5L/min, or greater than or equal to 25L/min to less than or equal to 35L/min. In other embodiments, the boil-off gas flows at a flow rate of greater than or equal to 60L/min to less than or equal to 70L/min.

In an embodiment, the flow rate of the gaseous vaporized fluid is greater than the flow rate of the layer precursor. Thus, in one or more embodiments, the layer precursor flows at the following flow rates: greater than or equal to 1.0L/min to less than or equal to 50L/min, such as greater than or equal to 3L/min to less than or equal to 5L/min, or greater than or equal to 25L/min to less than or equal to 35L/min. The flow rate of the vaporizing fluid and the flow rate of the layer precursor may be controlled such that the layer precursor is vaporized when contacted with the vaporizing fluid.

According to some embodiments, once the layer precursor is contacted with the vaporizing fluid to form a vaporized layer precursor, the vaporized layer precursor is decomposed by contacting the vaporized layer precursor with a flame. The flame may be formed by combusting a suitable combustion gas (e.g., oxygen, methane, ethane, propane, butane, natural gas, or mixtures thereof). Upon contact of the vaporized layer precursor with the flame, the layer precursor comes from the flameThe vaporized layer precursor is decomposed into atomic-level components, and the solvent is burned into a gas, e.g., hydrogen (H) ₂ ) Carbon dioxide (CO) ₂ ) And carbon monoxide (CO). This combustion provides a good dispersion of the elemental constituents of the ceramic precursor material in the gas. In one or more embodiments, the flame temperature is greater than or equal to 800K to less than or equal to 2500K. This enables easy guidance and deposition of the vaporized layer precursors onto the honeycomb body. It is to be understood that in embodiments, a flame may be used to decompose the layer precursor; however, in other embodiments, two or more flames may be used to decompose the layer precursors. In other embodiments, the vaporized layer precursor is not decomposed by a flame.

In one or more embodiments, the vaporized layer precursor, which is well dispersed in the fluid, is directed to the honeycomb body, for example, by using a wind tunnel or a pressure differential to direct the vaporized layer precursor to the honeycomb body. The vaporized layer precursors are thereby deposited on the honeycomb body. In some embodiments, the honeycomb body can have one or more channels plugged at one end (e.g., the first end 105 of the honeycomb body) during deposition of the vaporized layer precursor to the honeycomb body. In some embodiments, the plugged channels may be removed after the layer precursor is deposited. However, in other embodiments, the channels may remain plugged even after the layer precursor is deposited. The pattern of plugged channels of the honeycomb is not limited, and in some embodiments, the honeycomb body may plug all of the channels at one end. In other embodiments, only a portion of the channels of the honeycomb body may be plugged at one end. In such embodiments, the pattern of plugged and unplugged channels at one end of the honeycomb is not limited and can be, for example, a checkerboard pattern in which alternating channels at one end of the honeycomb are plugged. By plugging all or a portion of the channels at one end of the honeycomb during deposition of the vaporized layer precursor, the vaporized layer precursor can be uniformly distributed in the channels 110 of the honeycomb body 100.

In some embodiments, the vaporized layer precursor serves asThe amorphous phase is deposited onto the honeycomb. For example, as described above, in a decomposed layer precursor, the ceramic precursor material may be decomposed to an elemental level. When deposited onto the honeycomb body, the elemental constituents will mix together at the elemental level. For example, FIG. 3A is 5SiO deposited onto the surface of a honeycomb body ₂ ·2Al ₂ O ₃ Scanning Electron Microscope (SEM) image of amorphous phase of MgO decomposition layer precursor; FIG. 3B is a 2SiO deposition onto the surface of a honeycomb ₂ ·3Al ₂ O ₃ SEM image of amorphous phase of decomposed layer precursor; FIG. 3C is a 2SiO deposition onto the surface of a honeycomb ₂ ·5Al ₂ O ₃ SEM image of amorphous phase of 4MgO decomposition layer precursor; and FIG. 3D is Al deposited onto the surface of the honeycomb ₂ O ₃ SEM image of amorphous phase of MgO decomposition layer precursor. As can be seen from fig. 3A to 3D, respectively, on the honeycomb body, the particles at the element level are distributed in the amorphous phase. In this amorphous phase, the decomposed layer precursors that have been deposited onto the honeycomb have a porosity, as calculated (e.g., from the layer density and the density of the inorganic material of the layer), of greater than or equal to 95%, such as greater than or equal to 96%, or greater than or equal to 97%. In other embodiments, the amorphous phase decomposed layer precursor has a porosity greater than or equal to 98% or greater than or equal to 99%.

In some embodiments, the porosity and pore size of the amorphous vaporized layer precursor, and the porosity and pore size of the layers on the final honeycomb body, can be varied by the average particle size of the vaporized layers. The average particle size of the vaporized layer can be controlled by the flow rate of the layer precursors. For example, as shown in fig.4A through 4D, as the flow rate of the layer precursor increases, the average particle size of the vaporized layer precursor increases. FIG.4A is amorphous 5SiO deposited at a layer precursor flow rate of 3 mL/min ₂ ·2Al ₂ O ₃ 2 Transmission Electron Microscope (TEM) image of MgO decomposed layer precursor; FIG. 4B is amorphous 5SiO deposited at a layer precursor flow rate of 1 mL/min ₂ ·2Al ₂ O ₃ TEM image of MgO-decomposed layer precursor; FIG. 4C is amorphous 2SiO deposited at a layer precursor flow rate of 1 mL/min ₂ ·3Al ₂ O ₃ TEM images of the decomposed layer precursors; and FIG. 4D is amorphous 5SiO deposited using a two flame process with two flames having a layer precursor flow rate of 1 mL/min ₂ ·2Al ₂ O ₃ 2 MgO-decomposed layer precursor and amorphous 2SiO ₂ ·3Al ₂ O ₃ TEM image of the decomposed layer precursor. As shown in fig.4A to 4D, the elements of the decomposed layer precursor are mixed at an atomic level, forming a homogeneous phase having a particle size that varies depending on the flow rate of the layer precursor. However, in embodiments, the mean particle size of the vaporized layer precursor is greater than or equal to 5nm to less than or equal to 3 μm, such as greater than or equal to 100nm to less than or equal to 3 μm, or greater than or equal to 200 μm to less than or equal to 1 μm. In other embodiments, the average particle size of the vaporized layer precursor is greater than or equal to 15nm to less than or equal to 500nm, such as greater than or equal to 20nm to less than or equal to 200nm, or greater than or equal to 25 μm to less than or equal to 100nm.

As described above, chemical durability and physical stability may be imparted to layers on the walls of a honeycomb body according to some embodiments disclosed and described herein. To improve these properties, in one or more embodiments, after it is deposited onto the honeycomb body, the vaporized layer precursors can be sintered or otherwise bonded to the honeycomb body to form a layer as a crystalline phase that coats at least a portion of the honeycomb body. According to an embodiment, sintering the vaporized layer precursor includes heating the vaporized layer precursor to a temperature greater than or equal to 950 ℃ to less than or equal to 1150 ℃, such as greater than or equal to 1000 ℃ to less than or equal to 1100 ℃, greater than or equal to 1025 ℃ to less than or equal to 1075 ℃, or about 1050 ℃, after it is deposited onto the honeycomb body. In some embodiments, the duration of sintering is greater than or equal to 20 minutes to less than or equal to 2.0 hours, for example, greater than or equal to 30 minutes to less than or equal to 1.5 hours, or greater than or equal to 45 minutes to less than or equal to 1.0 hours. After the vaporized layer precursors are sintered to form the honeycomb, the layers are in a crystalline phase. For example, FIG. 5A is a sintered crystalline phase 5SiO deposited onto a honeycomb body ₂ ·2Al ₂ O ₃ 2MgO potterySEM image of the ceramic layer; FIG. 5B is a sintered crystalline phase 2SiO deposited onto a honeycomb body ₂ ·3Al ₂ O ₃ SEM image of ceramic layer; FIG. 5C is sintered crystalline phase 2SiO deposited onto a honeycomb body ₂ ·5Al ₂ O ₃ SEM image of 4MgO ceramic layer; FIG. 5D shows sintered crystalline phase Al deposited onto honeycomb ₂ O ₃ SEM image of MgO ceramic layer. According to an embodiment, the sintered crystalline phase layer has a porosity of greater than 90%, such as greater than or equal to 91% or greater than or equal to 92%, as measured by SEM. In other embodiments, the porosity of the sintered crystalline phase layer is greater than or equal to 93%, such as greater than or equal to 94% or greater than or equal to 95%. In other embodiments, the porosity of the sintered crystalline phase layer is greater than or equal to 96%, such as greater than or equal to 97% or greater than or equal to 98%.

According to one or more embodiments of the present disclosure, particulate filters are characterized by filtration efficiency, which is representative of their ability to remove certain particulate fractions from an incoming gas stream. The particles may be characterized by their mass or number concentration. These two values are typically closely related. Using universal concentration C _Granules (the unit is the mass or quantity of particles per unit volume), the filtration efficiency FE is generally obtained from the following equation:

equation (1):

the experimental measurement of filtration efficiency has different modes. A general laboratory equipment set-up is shown in figure 20. A common laboratory apparatus includes: a gas supply (e.g., air; regulated to define a flow rate), a particle generator (e.g., one that generates soot particles at a certain rate and concentration), a filter sample to be tested, and two particle analyzers at the inlet and outlet of the filter sample.

The experiment was performed at a controlled temperature (e.g., room temperature). As used herein, "room temperature" refers to a temperature of 20 ℃.During the experiment, the gas flow was adjusted to a constant flow rate. Then, particles are added to the gas. On the filter sample, some fraction of the particles were removed by filtration, which was measured as the difference between the inlet and outlet particle concentrations. An example of such an experiment is shown in fig. 21, plotted against a conventional sample (comparative example) for two experimental samples a and B made according to embodiments described herein. In the example shown, the particles are soot particles produced on a soot generator at a volumetric flow rate of 21m ³ H is used as the reference value. The test was performed at room temperature and atmospheric pressure. The filtration efficiency calculated from the inlet and outlet concentrations according to equation (1) is plotted against the experimental time. At time t =0s, the particle dose was started and the filtration efficiency was recorded. Different filtration efficiency values were observed for different filter samples.

As shown in fig. 21, the filtration efficiency increased with time in all cases. The reason for this is that the accumulated particles themselves (in this case soot) act as a filter medium, enhancing the overall efficiency. To more effectively address this situation, it is helpful to plot the filtering as a function of the mass of soot accumulated (rather than time). The soot mass is obtained as the difference in mass between the soot entering the filter and the soot leaving the filter integrated over time. In fig. 22, data from fig. 21 is provided in this form.

The filtration efficiency at the start (time equal to t =0s or 0g/L soot load) is commonly referred to as "clean" or "fresh" filtration efficiency and is determined only by the characteristics of the filter sample. Based on filtration theory, the filtration process is performed based on different mechanisms (mainly depending on particle size). A common model for describing filter media is the collective concept of unit collectors. For soot produced by the soot generator of the experiments described above, the dominant filtering mechanism was based on brownian motion of small soot particles. Collecting efficiency eta of unit collector based on Brownian motion mechanism _BM Can be described as:

equation (2)

A _S Is a parameter which depends primarily on the porosity ε, and Pe _i Is the peclet number. Peclet number and fluid velocity u in the pore space _w Epsilon and diffusion coefficient D of collector diameter dc and Brownian motion _BM The ratio of the two is proportional.

Equation (3)

Particle size d incorporating this collection mechanism by Brownian diffusion coefficient _s Dependence on temperature T, D _BM ～(T/d _s ² ). Combining all parameters dependent on the microstructure of the filter medium into a single variable K _{Microstructure} Equation (2) can be rewritten as equation (4):

equation (4)

The fluid velocity u being determined by dividing the volumetric flow rate by the cross-sectional area or the filter area _w . Thus, in addition to the microstructural characteristics, the filtration performance is directly proportional to the filtration area of the filter at a given flow rate and particle size. Thus, to compare materials with different microstructures, the filtration efficiency was normalized with respect to the filtration area. For a honeycomb wall-flow filter with alternately plugged channels, the filtration surface area FSA (in m) can be obtained from equation (5) ² )：

Equation (5):

in equation (5), GSA is the geometric surface area per unit filter volume, and V _Filter Is the volume of the filter sample. Factor 1-2 derives from the fact that: only half of the channels represent inlet channels through which gas enters and then flows through the porous filter wall. The filtration area (or total filtration) will be the total inlet cell area + the total outlet cell area = the total area. In other words, in equation (5), if the total inlet cell path area = the total outlet cell path area, the total inlet cell path area may be calculated by dividing the total area by 2. However, if the total inlet cell area is not equal to the total outlet cell area, the denominator in the equation may need to be modified to reflect this.

In addition to filtration performance, filters are typically characterized by their resistance to flow, typically referring to the pressure drop across the sample for a given gas volumetric flow rate. Generally, higher filtration performance is consistent with increased pressure drop or resistance to flow. For application considerations, it is generally desirable to have as low a pressure drop as possible, since pressure drop generally means pumping losses. In automotive applications, this results in a reduction in the power available to propel the vehicle or a reduction in fuel efficiency.

The pressure drop behavior of a filter sample is typically evaluated by measuring the pressure difference upstream and downstream of the filter sample at a given volumetric flow rate. In laboratory measurements, this can be done at room temperature and at different flow rates. In fig. 24, an example of a pressure drop measurement is shown. Plotted are the pressure differentials across filter samples at different volumetric flow rates for several experimental examples prepared according to the examples described in the present disclosure versus the commercially available wall-flow honeycomb particulate filter, both bare and containing a catalytic coating. The test was performed at room temperature. As characteristic values, the pressure drop determined in these tests was used as the highest sought flow rate, 357m under standard conditions ³ /h。

The filtration efficiency and pressure drop performance described above were tested on a wide range of filter samples from the prior art and several inventive samples having composite microstructures. For filtration, the initial or clean filtration efficiency (in%) was considered, as well as normalized by the filtration surface area of each sample. At 357m ³ The highest flow rate/h evaluates the pressure drop.

In fig. 24, data obtained from commercially available wall-flow honeycomb particulate filters (comparative examples) and samples made according to the examples described herein are summarized. Commercially available wall-flow honeycomb particulate filters (comparative examples) included several uncoated filter samples (having different microstructures and compositions) and filters coated with different catalytic washcoats (washcoats). As shown in fig. 24, examples prepared according to the present disclosure were located in different regions of the filter-pressure drop performance space of the graph, i.e., above the dashed line shown in fig. 24. The dotted line described by equation (6) may be defined as:

equation (6): (filtration efficiency/filtration area) A + B x (clean pressure drop)

Filtration efficiency means the clean or initial filtration efficiency (in%, 21 m) ³ H and room temperature), the unit of the filtration area is m ² And 357m at room temperature ³ The clean pressure drop was measured/h. Constants a and B are defined as follows:

A＝35％/m ² ；B＝9％/(m ² kPa)。

according to one or more embodiments, the particulate filter prepared according to the embodiments described herein advantageously exhibits a high filtration efficiency (normalized with respect to the filtration area of the inlet channel). Thus, according to one or more embodiments, the particulate filter described herein provides high filtration efficiency in the fresh (new) state immediately after installation into a vehicle in a car manufacturing facility. In some embodiments, this high filtration efficiency provides a low pressure drop.

While the claims of the present disclosure are not limited to a particular theory, it is believed that the pressure drop of the particulate filter includes 5 major factors. These factors include the compression and expansion of the gas flowing at the inlet and outlet of the filter, the frictional losses of the gas flowing along the inlet and outlet channels, and the pressure drop of the gas stream flowing through the porous channel walls.

Overall, the pressure drop across the filter is influenced by macroscopic geometrical parameters, such as: the diameter of the elements, the length, the hydraulic diameter of the channels and the open face area, as well as being influenced by the permeability of the porous filter walls. The latter is the only material property and is defined by the microstructure, for example: porosity, effective pore size, and pore connectivity. Since the gas flowing through the pores is laminar, the frictional losses on the walls are determined by the overall path through the porous walls.

The inlet and outlet contributions to the pressure drop can be described as follows:

equation (7):

Δ p is the pressure drop, ρ _g Is the gas density, Q is the volumetric flow rate, V _Filter Is the filter volume, L is the filter length, OFA is the open face area of the filter, and ζ _Into And ζ _{Go out} Empirical compression and expansion coefficients, respectively.

For the pressure drop within the filter, the equation provided by equation (26) in SAE technical paper 2003-01-0842 may be used, presented herein as equation (8).

Equation (8):

the new variable μ is the dynamic viscosity, Q _eff Is the effective volumetric flow rate, d _h Is the hydraulic channel diameter, t _w Is wall thickness, F is friction factor (F =28.45 for square channel), and κ _{Is effective} Is the effective permeability of the wall. The difference in effective volumetric flow rate from the total flow rate is a factor that accounts for the flow rates distributed along the inlet and outlet channels. Empirically found, Q _eff =1.32 × q provides a better description of the experimental results.

The total pressure drop measured in the experiment will be the sum of the contributions described by equations (7) and (8). In equations (7) and (8), all parameters are known and can be easily determined except for the effective permeability of the wall material.

Equations (7) and (8) may be employed,extraction of effective Permeability κ from Experimental data _{Is effective} . For this purpose, the pressure drop due to inlet compression and outlet expansion (eq. 7) is subtracted from the experimental pressure drop value, providing eq (9).

Equation (9): Δ p _(2,3,4) ＝Δp _{Experiment of} –Δp _(1,5)

Combining equation (9) and equation (8), and solving for the effective wall permeability κ _{Is effective} Obtaining:

equation (10):

can generally be determined by the porosity ε and the effective median pore diameter D ₅₀ The product of the squares of (a) and (b) divided by 66.7 describes in a relatively good way the permeability k of the porous walls of the extruded honeycomb body ₀ The porosity ε and the effective median pore diameter D ₅₀ Are all determined by mercury porosimetry:

equation (11):

if the permeability is κ ₀ The "as-extruded" bottom wall portion of the porous wall of (a) is coated or otherwise modified to change permeability to a new effective permeability value (κ) _{Is effective} ) This can be determined, for example, using equation (10) from the experimental pressure drop value. This change in permeability relative to the permeability of the bottom wall portion of the just-extruded honeycomb wall can also be described by the "Normalized Permeability Value (NPV)" which describes the ratio of the effective permeability relative to the permeability of the unmodified original microstructure:

equation (12): NPV = κ _{Is effective} /(εD ₅₀ ² /66.7) _{Bare chip}

The Δ p used to determine the filter sample can be estimated by measuring the pressure difference upstream and downstream of the filter sample at a given volumetric flow rate _{Experiment of} Experimental pressure drop measurements of (2). In the laboratoryIn the measurement, this can be done at room temperature and at different flow rates. In fig. 23, an example of a pressure drop measurement is shown. The pressure difference over the filter sample at different volumetric flow rates is plotted. The test was performed at room temperature. As characteristic values, the pressure drop determined in these tests was used as the highest sought flow rate, 357m under standard conditions ³ /h。

As discussed above, particulate filters are characterized by filtration efficiency, which is representative of their ability to remove certain particulate fractions from an incoming gas stream. The particles may be characterized by their mass or number concentration. These two values are typically closely related. Using a universal concentration C _Granules (the unit is the mass or quantity of particles per unit volume), the filtration efficiency FE is usually obtained by listening to equation (1) above.

The protocol for the general laboratory equipment is shown schematically in fig. 20, testing a particulate filter at room temperature at a constant flow rate, and then adding particles to the gas. On the filter sample, some fraction of the particles were removed by filtration, which was measured as the difference between the inlet and outlet particle concentrations. An example of such an experiment is shown in fig. 21, plotted against a conventional sample (comparative example) for two experimental samples a and B made according to embodiments described herein. In the example shown, the particles are soot particles on a soot generator at a volumetric flow rate of 21m under standard conditions ³ H is used as the reference value. The test was completed at room temperature. The filtration efficiency calculated from the inlet and outlet concentrations according to equation (1) is plotted against the experimental time. At time t =0s, the particle dose was started and the filtration efficiency was recorded. Different filtration efficiency values were observed for different filter samples.

As mentioned above, the filtration efficiency at the start (time equal to t =0s or 0g/L soot load) is generally referred to as "clean" or "fresh" filtration efficiency and is determined only by the characteristics of the filter sample. Based on filtration theory, the filtration process is performed based on different mechanisms (mainly depending on particle size). A common model for describing filter media is the concept of a collection of unit collectors. For soot generated by the soot generator of the experiments described above, the dominant filtering mechanism was based on brownian motion of small soot particles. Collecting efficiency eta of unit collector based on Brownian motion mechanism _BM Can be described by equation (2). As described above, the Peclet number and the fluid velocity u in the pore space _w Epsilon and diffusion coefficient D of collector diameter dc and Brownian motion _BM The ratio is proportional, as shown in equation (3) above.

SAE technical paper 2012-01-0363 explains that for uncoated extruded filters with "random" porous microstructure, the clean filtration efficiency will be related to the filtration performance parameter a _Filtration Related to this, which is proportional to the microstructure and macro-filter properties, equation (13):

equation (13)

As a new variable, equation (13) has CPSI as the cell density of the filter structure. The clean filtration efficiency can be plotted against this filter characteristic parameter (A) _Filtration ) Correlation between the efficiency of clean filtration on the Y-axis and the characteristic parameter of filtration (A) _Filtration ) On the X-axis.

The contributions from the microstructure parameter, porosity and median pore diameter can be combined into an effective microstructure factor, EMF. For materials with unknown effective porosity and median pore size, this new parameter can be used to characterize the effective properties of the microstructure. This variant also allows taking into account the actual microstructure, i.e. the filtration does not necessarily take place along the entire length of the holes in the filter wall, but rather locally to a greater extent at the locations where conditions exist that are favorable for the collection and deposition of particles, for example channels with narrow openings ("necks"). Once some of the particles are collected, they further narrow the pore neck, further accelerating the filtration process. Thus, the new parameters enable the consideration of microstructures that are heterogeneous and do not have a random pore design.

Similar to what is done for pressure drop, not only is the new microstructure parameter EMF taken into account, but it is also standardized, which is useful for the properties of the base microstructure of the bottom wall portion of the freshly extruded filter body with random microstructure. For the latter, the resulting EMF is the porosity ε ^0.43 Median pore diameter divided by the power of 5/3D ₅₀ In-line with the above and (4) the ratio. By this normalization, a new Normalized Microstructural Filter Value (NMFV) is obtained for describing the filtering properties of the microstructure, as equation (14): NMFV = EMF/(ε) ^0.43 /D ₅₀ ^5/3 ) _{Bottom wall properties} 。

According to one or more embodiments, a particulate filter is provided that achieves advantageous (e.g., high) Normalized Permeability Values (NPV), while also providing an increase in Normalized Microstructural Filtration Values (NMFV), e.g., a material that provides low pressure drop (variation) in combination with increased clean filtration.

The filtration efficiency and pressure drop performance were tested as described above for a wide range of filter samples from the prior art and several samples made according to the present disclosure having a composite microstructure defining the porous wall surfaces of the inlet channels, i.e., the inlet channels comprising a deposit of filtration material according to one or more embodiments described herein. For filtration, consider 21m ³ Initial or clean filtration efficiency in% in the case of/h. At 357m ³ The pressure drop was evaluated at the maximum flow rate/h and room temperature.

Reference examples (e.g., commercially available filters) and methods according to the present disclosureThe performance characteristics of the examples prepared by the embodiments of the disclosure are plotted. The data can be examined by plotting Normalized Microstructural Filter Values (NMFV) on the Y-axis and clean filters on the X-axis. For commercially available gasoline particulate filters and particulate filters (black diamonds) prepared according to examples of the present disclosure, a more useful plot of Normalized Permeability Values (NPV) on the Y-axis and Normalized Microstructural Filtration Values (NMFV) on the X-axis is shown in fig. 25. Fig. 25 shows an example of a particulate filter made in accordance with the present disclosure, while exhibiting: (1) NPV greater than 0.2, and (2) NMFV greater than 2. None of the commercially available gasoline particulate filters tested meet these criteria at the same time. Normalized microstructural filter value NMFV = EMF/(epsilon) ^0.43 /D ₅₀ ^5/3 ) _{Bottom wall properties} Is 2 or more, and the normalized penetration value NPV = κ _{Is effective} /(εD ₅₀ ² /66.7) _{Bottom wall properties} A range of 0.2 or greater is clearly novel and unique to the particulate filter of the present invention. Particulate filters that occupy this range, where both (1) NPV values greater than 0.2, and (2) NMFV values greater than 2, advantageously exhibit high filtration efficiency. Thus, according to one or more embodiments, the particulate filter described herein provides high filtration efficiency in a fresh (new) state immediately after installation into a vehicle in a car manufacturing plant. In some embodiments, this high filtration efficiency provides a low pressure drop.

Honeycomb bodies and methods of making honeycomb bodies are described herein. In an embodiment, the honeycomb body comprises a layer on at least one surface of the honeycomb body. In embodiments, the layer has a crystalline structure, a high porosity (e.g., greater than 90%), and the layer is applied as a thin layer, e.g., greater than or equal to 0.5 μm to less than or equal to 10 μm thick. It should be understood that in the various embodiments described above, the "honeycomb" may be a ceramic "honeycomb" and the "layer" may be a ceramic "layer".

Several embodiments disclosed and described herein are now provided.

1. A honeycomb body, comprising:

a porous ceramic honeycomb structure comprising: a first end, a second end, and a plurality of walls having wall surfaces defining a plurality of internal channels; and

a porous inorganic layer disposed on one or more of the wall surfaces, wherein

The porosity of the porous inorganic layer is greater than 90%, and

the average thickness of the porous inorganic layer is 0.5 μm or more and 30 μm or less.

2. The honeycomb body according to embodiment 1, wherein the porous inorganic layer has an average thickness of 20 μm or less.

3. The honeycomb body according to

embodiment

1 or 2, wherein the porous inorganic layer has an average thickness of 10 μm or less.

4. The honeycomb body according to any one of embodiments 1-3, wherein the porous inorganic layer comprises an oxide ceramic or an aluminum silicate.

5. The honeycomb body according to any one of embodiments 1-4, wherein the porous inorganic layer covers at least 70% of the wall surface.

6. The honeycomb body according to any one of embodiments 1-5, wherein the porous inorganic layer covers at least 90% of the wall surfaces.

7. The honeycomb body of embodiment 1, wherein the first end and the second end are separated by an axial length and the porous inorganic layer extends at least 60% along the axial length.

8. The honeycomb body according to any one of embodiments 1-7, wherein the porous inorganic layer extends at least 60% of the distance between the first end and the second end.

9. The honeycomb body according to any one of embodiments 1-8, wherein greater than 90% of the porous inorganic layer is disposed as a continuous coating on the wall surface.

10. The honeycomb body according to any one of embodiments 1-9, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 50%.

11. The honeycomb body according to any one of embodiments 1-10, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 55%.

12. The honeycomb body according to any one of embodiments 1-11, wherein the porous ceramic honeycomb structure has a porosity of 50% or more and 70% or less.

13. The honeycomb body according to any one of embodiments 1-12, wherein the porous ceramic honeycomb structure has a bulk median pore diameter of greater than or equal to 10 μm.

14. The honeycomb body according to any one of embodiments 1-13, wherein the porous ceramic honeycomb structure has a bulk median pore diameter of greater than or equal to 15 μm.

15. The honeycomb body according to any one of embodiments 1-14, wherein the porous ceramic honeycomb structure has a bulk median pore diameter of greater than or equal to 8 μ ι η to less than or equal to 25 μ ι η.

16. The honeycomb body according to any one of embodiments 1-15, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 35%.

17. The honeycomb body according to any one of embodiments 1-16, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 40%.

18. The honeycomb body according to any one of embodiments 1-15, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 35% to less than or equal to 60%.

19. The honeycomb body according to any one of embodiments 1-18, wherein the porous ceramic honeycomb structure has a surface median pore diameter of greater than or equal to 8 μm.

20. The honeycomb body according to any one of embodiments 1-19, wherein the porous ceramic honeycomb structure has a surface median pore diameter of greater than or equal to 10 μm.

21. The honeycomb body according to any one of embodiments 1-19, wherein the porous ceramic honeycomb structure has a surface median pore diameter of greater than or equal to 8 μ ι η to less than or equal to 20 μ ι η.

22. The honeycomb body according to any one of embodiments 1-21, wherein the porous inorganic layer has a porosity greater than 95%.

23. The honeycomb body of any one of embodiments 1-22, wherein the porous inorganic layer has a porosity of 98% or less.

24. The honeycomb body according to any one of embodiments 1-23, wherein the porous inorganic layers have an average thickness of greater than or equal to 1 μm to less than or equal to 20 μm.

25. The honeycomb body according to any one of embodiments 1-24, wherein the porous inorganic layers have an average thickness of greater than or equal to 1 μ ι η to less than or equal to 10 μ ι η.

26. The honeycomb body according to any one of embodiments 1-25, wherein the porous inorganic layers have a median pore diameter of greater than or equal to 0.1 μm to less than or equal to 5 μm.

27. The honeycomb body according to any one of embodiments 1-26, wherein the porous inorganic layers have a median pore diameter of greater than or equal to 0.1 μm to less than or equal to 4 μm.

28. The honeycomb body according to any one of embodiments 1-27, wherein the porous inorganic layer comprises particles having an average particle size of greater than or equal to 5nm to less than or equal to 3 μm.

29. The honeycomb body according to any one of embodiments 1-27, wherein the porous inorganic layer comprises particles having an average particle size of greater than or equal to 100nm to less than or equal to 3 μm.

30. The honeycomb body according to any one of embodiments 1-27, wherein the porous inorganic layer comprises particles having an average particle size of greater than or equal to 200nm to less than or equal to 1 μm.

31. The honeycomb body according to any one of embodiments 1-29, wherein the porous inorganic layer comprises at least one of: alumina, mullite or Al ₂ O ₃ ) _x (SiO ₂ ) _y Wherein x is equal to 2 or 3 and y is equal to 1 or 2, and the average particle size is greater than or equal to 5nm to less than or equal to 3 μm.

32. The honeycomb of embodiment 31, wherein the porous inorganic layers have an average particle size of greater than or equal to 100nm to less than or equal to 3 μm.

33. The honeycomb of embodiment 31, wherein the porous inorganic layers have an average particle size of greater than or equal to 200nm to less than or equal to 1 μm.

34. The honeycomb body according to any one of embodiments 1-27, wherein the porous inorganic layer comprises alumina having an average particle size of greater than or equal to 5nm to less than or equal to 3 μm.

35. The honeycomb body of embodiment 34, wherein the porous inorganic layer comprises alumina having an average particle size of greater than or equal to 100nm to less than or equal to 3 μ ι η.

36. The honeycomb body of embodiment 34, wherein the porous inorganic layer comprises alumina having an average particle size of greater than or equal to 200nm to less than or equal to 3 μ ι η.

37. The honeycomb body according to any one of embodiments 1-30, wherein the porous inorganic layer comprises a member selected from the group consisting of: siO 2 ₂ 、Al ₂ O ₃ 、MgO、ZrO ₂ 、CaO、TiO ₂ 、CeO ₂ 、Na ₂ O, pt, pd, ag, cu, fe, ni, and mixtures thereof.

38. The honeycomb body of embodiment 37, wherein the porous inorganic layer has an amorphous structure.

39. The honeycomb of embodiment 37, wherein the porous inorganic layer has a crystalline structure.

40. The honeycomb body according to any one of embodiments 1-39, wherein the porous inorganic layer has a permeability of greater than or equal to 10 ^-15 m ² 。

41. The honeycomb body according to any one of embodiments 1-39, wherein the porous inorganic layer has a permeability of greater than or equal to 10 ^-14 m ² 。

42. The honeycomb body according to any one of embodiments 1-39, wherein the porous inorganic layer has a permeability of greater than or equal to 10 ^-13 m ² 。

43. The honeycomb body according to any one of embodiments 1-39, wherein the porous inorganic layer has a permeability of greater than or equal to 10 ^-12 m ² 。

44. The honeycomb body according to any one of embodiments 1-43, wherein the porous inorganic layer is free of cracks having a width greater than 5 μm and a length greater than 1 mm.

45. The honeycomb body according to any one of embodiments 1-44, wherein at least a portion of the internal channels are plugged at the first end of the porous ceramic honeycomb body.

46. The honeycomb body according to any one of embodiments 1-45, wherein at least a portion of the internal channels are plugged at the second end of the porous ceramic honeycomb body.

47. The honeycomb body according to any one of embodiments 1-46, wherein the honeycomb body has an initial filtration efficiency of greater than or equal to 75% at 21Nm ³ Measured as 120nm particles per hour.

48. The honeycomb body according to any one of embodiments 1-47, wherein the honeycomb body has an initial filtration efficiency of greater than or equal to 90%.

49. The honeycomb body according to any one of embodiments 1-45 wherein the honeycomb body has a filtration efficiency of 70% or greater as measured at 120nm particles at a velocity of 1.7 m/sec and a soot load of 0.01 g/L.

50. The honeycomb body of embodiment 49, wherein the honeycomb body has a filtration efficiency of greater than or equal to 80%.

51. The honeycomb body of embodiment 50, wherein the honeycomb body has a filtration efficiency of greater than or equal to 90%.

52. The honeycomb of embodiment 51, wherein the honeycomb has a measured filtration efficiency of greater than or equal to 95%.

53. The honeycomb of embodiment 45, wherein the maximum pressure drop across the honeycomb is less than or equal to 20%.

54. The honeycomb of embodiment 45, wherein the maximum pressure drop across the honeycomb is less than or equal to 10%.

55. The honeycomb body according to any one of embodiments 1-54, wherein the porous inorganic layer comprises synthetic mullite.

56. The honeycomb body according to any one of embodiments 1-55, wherein the porous inorganic layer is sintered to one or more of the wall surfaces.

57. A ceramic filter article, comprising:

a porous ceramic body comprising a honeycomb structure comprising a plurality of walls, each wall comprising a porous ceramic bottom wall portion, wherein a first set of walls is present, and wherein each of the first set of walls further comprises a substitute retentate layer (retentate layer) forming an outermost wall layer defining a first set of channels, wherein the substitute retentate layer has a porosity greater than 90% and an average thickness greater than or equal to 0.5 μ ι η and less than or equal to 30 μ ι η.

58. The ceramic filter article of embodiment 57, wherein the replacement retentate layer comprises a first porous inorganic layer.

59. The ceramic filter article of embodiment 57, wherein the replacement retentate layer comprises a first porous organic layer.

60. The ceramic filter article of embodiment 57, wherein the porous ceramic bottom wall portion comprises a primary base ceramic phase and the first porous inorganic layer comprises a primary first ceramic phase different from the base ceramic phase.

61. The ceramic filter article of embodiment 60, wherein the base ceramic phase comprises cordierite.

62. The ceramic filter article of embodiment 60, wherein the first ceramic phase comprises alumina or silica, or a combination thereof.

63. The ceramic filter article of embodiment 60, wherein the first ceramic phase is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

64. The ceramic filter of any of embodiments 58-63, wherein the first porous inorganic layer comprises synthetic mullite.

65. The ceramic filter of any of embodiments 58-63, wherein the first porous inorganic layer is sintered to the porous ceramic bottom wall portion.

66. A ceramic filter article, comprising:

a porous ceramic body comprising a honeycomb structure comprising a plurality of walls defining a plurality of channels, each wall comprising a porous ceramic bottom wall portion, wherein at least some of the walls comprise a first porous inorganic outer layer disposed on the porous ceramic bottom wall portion, the first porous inorganic outer layer providing a first outermost wall surface, wherein the plurality of walls intersect to define first channels surrounded by the first outermost wall surface,

wherein the first porous inorganic layer has a porosity of greater than 90% and an average thickness of greater than or equal to 0.5 μm and less than or equal to 30 μm.

67. The ceramic filter article of embodiment 66, wherein the walls further comprise a second outermost wall surface provided by the porous ceramic bottom wall portion, and the second outermost wall surface defines a plurality of second channels surrounded by the second outermost wall surface.

68. The ceramic filter article of embodiment 66, wherein at least a majority of the first channels are open at a first end of the porous ceramic body and sealed at a second end of the porous ceramic body, and wherein at least a majority of the second channels are open at the second end of the porous ceramic body and sealed at the first end of the porous ceramic body.

69. The ceramic filter article of embodiment 66, wherein at least some of the walls comprise a second porous inorganic outer layer disposed on the porous ceramic bottom wall portion, the second porous inorganic outer layer providing a second outermost wall surface, wherein the plurality of walls intersect to define a second channel surrounded by the second outermost wall surface.

70. The ceramic filter article of embodiment 66, wherein at least a majority of the first channels are open at the first end of the porous ceramic body and sealed at the second end of the porous ceramic body, and wherein at least a majority of the second channels are open at the second end of the porous ceramic body and sealed at the first end of the porous ceramic body.

71. The ceramic filter article of embodiment 66, wherein the porous ceramic bottom wall portion has a porosity of 30% to 70%.

72. The ceramic filter article of embodiment 66, wherein the porous ceramic bottom wall portion has a porosity of 30% to 70%.

73. The ceramic filter article of embodiment 66, wherein the first porous inorganic outer layer comprises flame deposited particles.

74. The ceramic filter article of embodiment 62, wherein the first porous inorganic outer layer comprises CVD particles.

75. The ceramic filter of any of embodiments 66-74, wherein the first porous inorganic layer comprises synthetic mullite.

76. The ceramic filter of any of embodiments 66-75, wherein the first porous inorganic layer is sintered to the porous ceramic bottom wall portion.

77. A ceramic filter article, comprising:

a porous ceramic body comprising a honeycomb structure comprising a plurality of walls, wherein at least some of the walls comprise opposing first and second surfaces and a bottom wall portion disposed between the first and second surfaces, and the plurality of walls intersect to define first channels through the first surface and second channels through the second surface, wherein at least the first surface or the second surface is at least partially provided by a porous inorganic layer disposed on the bottom wall portion, wherein the porosity of the porous inorganic layer is greater than 90%, and the average thickness of the porous inorganic layer is greater than or equal to 0.5 μ ι η and less than or equal to 30 μ ι η.

78. The ceramic filter article of embodiment 77, wherein both the first and second surfaces are at least partially provided by a porous inorganic layer disposed on the bottom wall portion.

79. The ceramic filter article of embodiment 77, wherein the porous inorganic layer is disposed on the inlet surface of at least some of the walls.

80. The ceramic filter article of embodiment 77, wherein the porous inorganic layer is disposed only on the inlet surfaces of at least some of the walls.

81. The ceramic filter article of embodiment 77, wherein the outlet surface is free of any porous inorganic layer.

82. The ceramic filter of any of embodiments 77-81, wherein the porous inorganic layer comprises synthetic mullite.

83. The ceramic filter of any of embodiments 77-82, wherein the porous inorganic layer is sintered to the bottom wall portion.

84. A particulate filter, comprising:

a honeycomb body comprising a plugged porous ceramic honeycomb structure comprising a plurality of intersecting porous walls arranged in a cell matrix, the porous walls comprising porous wall surfaces defining a plurality of channels extending from an inlet end to an outlet end of the structure, the plurality of channels comprising inlet channels sealed at or near the outlet end and having a surface area, and outlet channels sealed at or near the inlet end and having a surface area;

wherein one or more of the porous wall surfaces defining the inlet channels comprise a bottom wall portion and a deposit of filter material disposed on the bottom wall portion such that the porous wall surfaces defining at least a portion of the inlet channels comprise the deposit of filter material, forming a porous inorganic layer having a porosity greater than 90%;

wherein the honeycomb body comprises a total inlet Surface Area (SATOT) which is the sum of the surface areas of all porous walls defining the inlet channels;

wherein the particulate filter induces a pressure Drop (DP) for an air flow (aircfm) through the particulate filter at an air temperature (AIRTEMP), the air flow containing particles having an average size of 100 nm;

wherein, when the particulate filter contains less than 0.01 grams of particles per volume of the honeycomb structure in units of liters (g/L), the particulate filter traps particles carried by the air stream into the particulate filter having a flow rate of 21m at AIRTEMP = room temperature ³ Filtration Efficiency (FE) measured as/h such that FE/SATOT is greater than (9 x DP + 35) in units of%/m ² DP in kPa of 357m ³ Flow rate per hourMeasured and measured at AIRTEMP = room temperature; and

wherein the bottom wall portion comprises a first ceramic composition and the filter material deposit comprises a second ceramic composition, and the first and second ceramic compositions are different.

85. The particulate filter of embodiment 84, wherein the porous inorganic layer has an average thickness greater than or equal to 0.5 μ ι η and less than or equal to 30 μ ι η.

86. The particulate filter of embodiments 84 or 85, wherein the second ceramic composition comprises alumina or silica, or a combination thereof.

87. The particulate filter of embodiment 84 or 85, wherein the second ceramic composition is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

88. The particulate filter of embodiment 84 or 85, wherein the second ceramic composition is cordierite and the second ceramic composition is alumina.

89. The particulate filter of embodiment 76 or 77, wherein the porous inorganic layer comprises an oxide ceramic or an aluminum silicate.

90. The particulate filter of any one of embodiments 84-89, wherein the porous inorganic layer covers at least 70% of the porous wall surface.

91. The particulate filter of any one of embodiments 76-81, wherein the porous inorganic layer covers at least 90% of the porous wall surface.

92. The particulate filter of any of embodiments 84-89, wherein the inlet end and the outlet end are separated by an axial length, and the porous inorganic layer extends at least 60% along the axial length.

93. The particulate filter of any one of embodiments 84-89, wherein the porous inorganic layer extends at least 60% of the distance between the inlet end and the outlet end.

94. The particulate filter of any one of embodiments 84-89, wherein greater than 90% of the porous inorganic layer is disposed as a continuous coating on the porous wall surface.

95. The particulate filter of any one of embodiments 84-94, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 50% to less than or equal to 70%.

96. The particulate filter of any one of embodiments 84-95, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 10 μ ι η.

97. The particulate filter of any one of embodiments 84-95, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 15 μ ι η.

98. The particulate filter of any one of embodiments 84-95, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 8 μ ι η to less than or equal to 25 μ ι η.

99. The particulate filter of embodiment 84, wherein the deposit of filter material comprises synthetic mullite.

100. The ceramic filter of embodiment 84, wherein the filter material deposit is sintered to the porous ceramic bottom wall portion.

101. A particulate filter, comprising:

a honeycomb body comprising a plugged porous ceramic honeycomb structure comprising a plurality of intersecting porous walls comprising porous wall surfaces defining a plurality of channels extending from an inlet end to an outlet end of the structure, the plurality of channels comprising inlet channels sealed at or near the outlet end and having a surface area, and outlet channels sealed at or near the inlet end and having a surface area, the inlet and outlet channels defining a filtration zone;

wherein one or more of the porous wall surfaces defining the inlet channels comprise a bottom wall portion and a deposit of filter material disposed on the bottom wall portion such that the porous wall surfaces defining at least a portion of the inlet channels comprise the deposit of filter material, forming a porous inorganic layer having a porosity greater than 90%; and

wherein the particulate filter exhibits a per unit filter area (unit m) ² ) Is equal to or greater than a value of (a + B cleaning pressure drop), a and B being defined as a =35%/m ² And B = 9%/(m) ² kPa) on a particle filter with a soot load of less than 0.01g/L, at room temperature and 21m ³ Clean filtration efficiency was measured at a flow rate of/h and on a soot-free filter at 357m ³ The flow rate in/h measures the clean pressure drop.

102. The particulate filter of embodiment 101, wherein one or more of the porous wall surfaces defining the inlet channels comprises a bottom wall portion comprising a first ceramic composition and the deposit of filter material disposed on the bottom wall portion comprises a second ceramic composition, and the first and second ceramic compositions are different.

103. The particulate filter of embodiment 101, wherein the porous inorganic layer has an average thickness greater than or equal to 0.5 μ ι η and less than or equal to 30 μ ι η.

104. The particulate filter of embodiment 101, wherein the second ceramic composition comprises alumina or silica, or a combination thereof.

105. The particulate filter of embodiment 101, wherein the second ceramic composition is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

106. The particulate filter of embodiment 101, wherein the first ceramic composition is cordierite and the second ceramic composition is alumina.

107. The particulate filter of embodiment 101, wherein the porous inorganic layer comprises an oxide ceramic or an aluminum silicate.

108. The particulate filter of embodiment 101, wherein the porous inorganic layer covers at least 70% of the surface of the porous walls.

109. The particulate filter of embodiment 101, wherein the porous inorganic layer covers at least 90% of the surface of the porous walls.

110. The particulate filter of embodiment 101, wherein the inlet end and the outlet end are separated by an axial length and the porous inorganic layer extends at least 60% along the axial length.

111. The particulate filter of embodiment 106, wherein the porous inorganic layer extends at least 60% of the distance between the inlet end and the outlet end.

112. The particulate filter of embodiment 101, wherein greater than 90% of the porous inorganic layer is disposed as a continuous coating on the porous wall surface.

113. The particulate filter of embodiment 101, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 50% to less than or equal to 70%.

114. The particulate filter of embodiment 106, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 10 μ ι η.

115. The particulate filter of embodiment 101, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 15 μ ι η.

116. The particulate filter of embodiment 101, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 8 μ ι η to less than or equal to 25 μ ι η.

117. The particulate filter of embodiment 101, wherein the deposit of filter material comprises synthetic mullite.

118. The ceramic filter of embodiment 84, wherein the filter material deposit is sintered to the porous ceramic bottom wall portion.

119. A particulate filter, comprising:

a honeycomb body comprising a plugged porous ceramic honeycomb structure comprising a plurality of intersecting porous walls comprising porous wall surfaces defining a plurality of channels extending from an inlet end to an outlet end of the porous ceramic honeycomb structure, the plurality of channels comprising inlet channels sealed at or near the outlet end and having a surface area, and outlet channels sealed at or near the inlet end and having a surface area, the inlet channels and the outlet channels defining a filtration zone;

wherein one or more of the porous wall surfaces defining the inlet channels comprise a bottom wall portion and a deposit of filter material disposed on the bottom wall portion to provide a composite microstructure such that the porous wall surfaces defining at least a portion of the inlet channels comprise the deposit of filter material, forming a porous inorganic layer having a porosity of greater than 90%, and the composite microstructure has a porosity (ε) as measured by mercury porosimetry, a median pore diameter (D) as measured by mercury porosimetry ₅₀ ) Permeability factor (κ) and measured Effective Microstructural Factor (EMF),

wherein the composite microstructure is characterized by a normalized microstructure filter value NMFV = EMF/(ε) ^0.43 /D ₅₀ ⁵ ^/3 ) _{Bottom wall properties} Is 2 or more, and the normalized penetration value NPV = κ _{Is effective} /(εD ₅₀ ² /66.7) _{Bottom wall properties} Is 0.2 or greater.

120. The particulate filter of embodiment 119, wherein one or more of the porous wall surfaces defining the inlet channels comprises a bottom wall portion comprising a first ceramic composition and the deposit of filter material disposed on the bottom wall portion comprises a second ceramic composition, and the first and second ceramic compositions are different.

121. The particulate filter of embodiment 119, wherein the porous inorganic layer has an average thickness greater than or equal to 0.5 μ ι η and less than or equal to 30 μ ι η.

122. The particulate filter of embodiment 119, wherein the second ceramic composition comprises alumina or silica, or a combination thereof.

123. The particulate filter of embodiment 119, wherein the second ceramic composition is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

124. The particulate filter of embodiment 119, wherein the first ceramic composition is cordierite and the second ceramic composition is alumina.

125. The particulate filter of embodiment 119, wherein the porous inorganic layer comprises an oxide ceramic or an aluminum silicate.

126. The particulate filter of embodiment 119, wherein the porous inorganic layer covers at least 70% of the surface of the porous walls.

127. The particulate filter of embodiment 119, wherein the porous inorganic layer covers at least 90% of the porous wall surface.

128. The particulate filter of embodiment 119, wherein the inlet end and the outlet end are separated by an axial length and the porous inorganic layer extends at least 60% along the axial length.

129. The particulate filter of embodiment 119, wherein the porous inorganic layer extends at least 60% of the distance between the inlet end and the outlet end.

130. The particulate filter of embodiment 122, wherein greater than 90% of the porous inorganic layer is disposed as a continuous coating on the porous wall surface.

131. The particulate filter of embodiment 119, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 50% to less than or equal to 70%.

132. The particulate filter of embodiment 119, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 10 μ ι η.

133. The particulate filter of embodiment 119, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 15 μ ι η.

134. The particulate filter of embodiment 119, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 8 μ ι η to less than or equal to 25 μ ι η.

135. The particulate filter of embodiment 119, wherein 850Nm exposure to room temperature ³ The particulate filter exhibits a filtration efficiency variation of less than 5% after a high flow condition of air for 1 minute, and wherein the filtration efficiency variation is determined by measuring the difference between the number of soot particles introduced into the particulate filter and the number of soot particles leaving the particulate filter before and after exposure to the high flow condition, wherein the soot particles have a median particle size of 300nm, the soot particle concentration measured by a particle counter in an air stream flowing through the particulate filter at room temperature and a velocity of 1.7m/s being 500,000 particles/cm ³ 。

136. The particulate filter of embodiment 119, wherein the deposit of filter material comprises synthetic mullite.

137. The ceramic filter of embodiment 119, wherein the deposit of filter material is sintered to the porous ceramic bottom wall portion.

138. A particulate filter, comprising:

wherein one or more of the porous wall surfaces defining the inlet channels comprise a bottom wall portion and a deposit of filter material disposed on the bottom wall portion,

wherein the deposit of filter material is disposed on the bottom wall portion to provide a porous inorganic layer having a porosity greater than 90%,

and wherein, upon exposure to room temperature, 850Nm ³ After 1 minute of high flow condition of air/h, the particulate filter exhibited a smallA filtration efficiency change of at 5%, and wherein the filtration efficiency change is determined by measuring the difference between the number of soot particles introduced into the particulate filter and the number of soot particles leaving the particulate filter before and after exposure to high flow conditions, wherein the soot particles have a median particle size of 300nm and the soot particle concentration measured by a particle counter in an air stream flowing through the particulate filter at room temperature and a velocity of 1.7m/s is 500,000 particles/cm ³ 。

139. The particulate filter of embodiment 138, wherein one or more of the porous wall surfaces defining the inlet channels comprises a bottom wall portion comprising a first ceramic composition and the deposit of filter material disposed on the bottom wall portion comprises a second ceramic composition, and the first and second ceramic compositions are different.

140. The particulate filter of embodiment 138, wherein the porous inorganic layer has an average thickness greater than or equal to 0.5 μ ι η and less than or equal to 30 μ ι η.

141. The particulate filter of embodiment 138, wherein the second ceramic composition comprises alumina or silica, or a combination thereof.

142. The particulate filter of embodiment 138, wherein the second ceramic composition is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

143. The particulate filter of embodiment 138, wherein the first ceramic composition is cordierite and the second ceramic composition is alumina.

144. The particulate filter of embodiment 138, wherein the porous inorganic layer comprises an oxide ceramic or an aluminum silicate.

145. The particulate filter of embodiment 138, wherein the porous inorganic layer covers at least 70% of the surface of the porous walls.

146. The particulate filter of embodiment 138, wherein the porous inorganic layer covers at least 90% of the surface of the porous walls.

147. The particulate filter of embodiment 119, wherein the inlet end and the outlet end are separated by an axial length and the porous inorganic layer extends at least 60% along the axial length.

148. The particulate filter of embodiment 138, wherein the porous inorganic layer extends at least 60% of the distance between the inlet end and the outlet end.

149. The particulate filter of embodiment 122, wherein greater than 90% of the porous inorganic layer is disposed as a continuous coating on the porous wall surface.

150. The particulate filter of embodiment 138, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 50% to less than or equal to 70%.

151. The particulate filter of embodiment 138, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 10 μ ι η.

152. The particulate filter of embodiment 138, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 15 μ ι η.

153. The particulate filter of embodiment 138, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 8 μ ι η to less than or equal to 25 μ ι η.

154. The particulate filter of embodiment 138, wherein the 850Nm exposure to room temperature ³ The particulate filter exhibits a filtration efficiency variation of less than 5% after 1 minute of high flow conditions of air, and wherein the filtration efficiency variation is determined by measuring the difference between the number of soot particles introduced into the particulate filter and the number of soot particles leaving the particulate filter before and after exposure to the high flow conditions, wherein the soot particles have a median particle size of 300nm, the soot particle concentration measured by a particle counter in an air stream flowing through the particulate filter at room temperature and a velocity of 1.7m/s being 500,000 particles/cm ³ 。

155. The particulate filter of embodiment 138, wherein the deposit of filter material comprises synthetic mullite.

156. The ceramic filter of embodiment 119, wherein the deposit of filter material is sintered to the porous wall surface.

157. A method of manufacturing a honeycomb body, the method comprising:

contacting the inorganic layer precursor with a gaseous carrier fluid;

depositing an inorganic layer precursor on a porous ceramic honeycomb structure by flowing a gaseous carrier fluid to the porous ceramic honeycomb structure, the porous ceramic honeycomb structure comprising a plurality of intersecting porous walls arranged in a cell matrix, the porous walls comprising porous wall surfaces defining a plurality of channels extending from an inlet end to an outlet end of the structure, the plurality of channels comprising inlet channels sealed at or near the outlet end and having a surface area, and outlet channels sealed at or near the inlet end and having a surface area; and

bonding an inorganic layer precursor to the porous ceramic honeycomb structure to form a porous inorganic layer, wherein

The porosity of the porous inorganic layer is greater than 90%, and

the porous inorganic layer has an average thickness of 0.5 μm or more and 30 μm or less.

158. The method of making a honeycomb according to embodiment 157, wherein the porous inorganic layer has an average thickness in the range from greater than or equal to 1 μm to less than or equal to 20 μm.

159. The method of making a honeycomb according to embodiment 157, wherein the porous inorganic layer has an average thickness in the range from greater than or equal to 1 μm to less than or equal to 10 μm.

160. The method of making a honeycomb according to any one of embodiments 157-159, wherein the inorganic layer precursor comprises a ceramic precursor material.

161. The method of making a honeycomb according to embodiment 160 wherein the inorganic layer precursor comprises a solvent.

162. The method of making a honeycomb according to embodiment 161 wherein the solvent is selected from the group consisting of: methoxyethanol, ethanol, water, xylene, methanol, ethyl acetate, benzene, and mixtures thereof.

163. The method of making a honeycomb according to embodiment 160 further comprising decomposing the inorganic layer precursor by contacting the inorganic layer precursor with a flame.

164. The method of making a honeycomb according to any one of embodiments 157-163, wherein bonding the inorganic layer precursor to the ceramic honeycomb comprises sintering the inorganic layer precursor.

165. The method of making a honeycomb of embodiment 164 wherein the sintering of the inorganic layer precursors is performed at a temperature of greater than or equal to 450 ℃ to less than or equal to 1150 ℃ for a duration of greater than or equal to 20 minutes to less than or equal to 12 hours.

166. The method of making a honeycomb according to embodiment 165 wherein the inorganic layer precursor is deposited onto the ceramic honeycomb body as an amorphous phase having a porosity of greater than or equal to 98%, and

after sintering of the inorganic layer precursor, an inorganic layer having a crystalline phase and a porosity greater than or equal to 95% is present on the ceramic honeycomb body.

167. The method of making a honeycomb according to any one of embodiments 157-163, wherein bonding the inorganic layer precursor to the ceramic honeycomb comprises applying moisture to the ceramic layer precursor.

168. The method of making a honeycomb according to any one of embodiments 157-163, wherein the ceramic layer precursor comprises a member selected from the group consisting of: tetraethyl orthosilicate, magnesium ethoxide and aluminum tri-sec-butoxide (III), trimethylaluminum, alCl ₃ 、SiCl ₄ 、Al(NO ₃ ) ₃ Aluminum isopropoxide, octamethylcyclotetrasiloxane, and mixtures thereof.

169. A method of manufacturing a honeycomb body, the method comprising:

contacting the inorganic layer precursor with a gaseous carrier fluid;

vaporizing the inorganic layer precursor to form a gaseous inorganic layer precursor;

exposing the gaseous inorganic layer precursor to a flame to produce layer precursor particles;

depositing layer precursor particles onto the ceramic honeycomb structure by flowing a gaseous carrier fluid onto the ceramic honeycomb structure; and

sintering inorganic layer precursor particles to a ceramic honeycomb body to form a porous inorganic layer, wherein

The porosity of the porous inorganic layer is greater than 90%, and

170. The method of making a honeycomb of embodiment 169 wherein the porous inorganic layer comprises an oxide ceramic or an aluminum silicate.

171. The method of making a honeycomb of embodiment 170 wherein the oxide ceramic comprises synthetic mullite.

Examples

Embodiments are further clarified by the following examples.

Example 1

Flame pyrolysis of liquid precursors. This example tests the chemical durability and physical stability of ceramic layers deposited on cordierite honeycombs. Layer precursors were formed from 2 parts tetraethylorthosilicate and 3 parts aluminum (III) tri-sec-butoxide in methoxyethanol/ethanol (1:1 by volume) solvent. The layer precursor was fed at a flow rate of 1 mL/min and contacted with an oxygen boil-off gas fed at a flow rate of 5L/min, which vaporized the layer precursor. The vaporized layer precursor is decomposed in a flame and then deposited as an amorphous phase layer. The following table 1 lists the properties of cordierite honeycombs:

TABLE 1

The decomposed layer precursors were then sintered by heating to 1150 ℃ for 30 minutes to form a crystalline phase ceramic layer on the cordierite honeycomb (i.e., honeycomb). For testing purposes, a soot generating device (CAST 2) was used in the presence of 350L/min (21 Nm) ³ At an air flow rate of/h), a flat result is obtainedParticles having a mean particle diameter of 120 nm. Table 2 below provides the filtration efficiencies of comparative example 1 for honeycombs without inorganic coating and example 1 for honeycombs with inorganic coating.

Table 2: filter Efficiency (FE) comparison

As shown in table 2, the filtration efficiency of example 1 was much higher than that of comparative example 1 when loaded with low soot. Accordingly, DPFs or GPFs having inorganic coatings according to embodiments disclosed and described herein do not require a time-consuming soot layer buildup process before the filter is able to achieve high filtration efficiencies (e.g., filtration efficiencies greater than 90%). FIG. 6 is a representative graph of filtration efficiency versus soot loading and illustrates the increased filtration efficiency by the addition of inorganic layers to a honeycomb body according to embodiments disclosed and described herein.

Fig. 7A and 7B schematically show the back pressures of example 1 and comparative example 1. FIG. 7A is back pressure (kPa) versus flow rate (Nm) of example 1 and comparative example 1 ³ H) graph of the relationship. As shown in fig. 7A, the relationship of the back pressure and the flow rate was very similar for both example 1 and comparative example 1. Thus, as shown in fig. 7A, when an inorganic layer according to embodiments disclosed and described herein is applied to a honeycomb body, there is no significant flow-rate related impairment of back pressure. FIG. 7B is a graph of back pressure (kPa) versus soot load level (g/L) for example 1 and comparative example 1. As shown in fig. 7B, the back pressure at each measured soot load showed that the back pressure of example 1 was less than comparative example 1. Thus, there is no significant back pressure penalty for using inorganic layers according to embodiments disclosed and described herein with various soot loadings.

Table 3 below shows various properties of the inorganic layer of example 1, and fig. 8A and 8B are SEM photographs of the inorganic layer taken at 5 μm and 1 μm magnifications, respectively, of example 1.

TABLE 3

/>

Example 2

Flame pyrolysis of the vapor precursor. Aluminum isopropoxide and octamethylcyclotetrasiloxane are used as xAl ₂ O ₃ ·ySiO ₂ A precursor of (2). The precursor is heated and the steam generated is N ₂ And (7) carrying. The composition of the as-deposited layer is controlled in a window of 1.5. Ltoreq. X/y. Ltoreq.2. The vaporized layer precursors decomposed in a flame and were then deposited as amorphous phase decomposed layer precursors on cordierite honeycombs having the properties listed in table 4.

TABLE 4

In Table 4, CPSI is Kong Daoshu per square inch and porosity is measured by mercury intrusion.

The decomposed layer precursors were then sintered by heating to 1150 ℃ for 30 minutes to form a crystalline phase ceramic layer on the cordierite honeycomb (i.e., honeycomb). Soot formation was performed according to example 1. Table 5 below provides the Filtration Efficiencies (FE) of comparative example 2, which is a honeycomb without an inorganic coating, and example 2, which is a honeycomb with an inorganic coating.

TABLE 5

/>

As shown in table 5, the filtration efficiency of example 2 was much higher than that of comparative example 2 when loaded with low soot. Accordingly, DPFs or GPFs having inorganic coatings according to embodiments disclosed and described herein do not require a time-consuming soot layer buildup process before the filter is able to achieve high filtration efficiencies (e.g., filtration efficiencies greater than 90%). FIG. 9 is a representative graph of filtration efficiency versus soot loading and illustrates the increased filtration efficiency by the addition of inorganic layers to a honeycomb body according to embodiments disclosed and described herein.

Fig. 10A and 10B schematically show the back pressures of example 2 and comparative example 2. FIG. 10A is back pressure (kPa) vs. flow Rate (Nm) of example 2 and comparative example 2 ³ H) graph of the relationship. As shown in fig. 10A, the relationship of the back pressure and the flow rate is very similar for both example 2 and comparative example 2. Thus, as shown in fig. 10A, when an inorganic layer according to embodiments disclosed and described herein is applied to a honeycomb body, there is no significant flow rate related impairment of backpressure. FIG. 10B is a graph of back pressure (kPa) versus soot load level (g/L) for example 2 and comparative example 2. As shown in fig. 10B, the back pressure at each measured soot load showed that the back pressure of example 2 was less than comparative example 2. Thus, there is no significant back pressure penalty for using inorganic layers according to embodiments disclosed and described herein with various soot loadings.

Table 6 below shows various properties of the inorganic layer of example 2, and fig. 11A and 11B are SEM photographs of the inorganic layer taken at 5 μm and 1 μm magnifications, respectively, of example 2.

TABLE 6

FIG. 12 shows an XRD scan of the as-deposited inorganic layer (decomposed layer precursor), showing the amorphous phase; and XRD scanning of the inorganic layer after sintering, which shows a crystalline phase ceramic layer with peaks consistent with the mullite standard pattern.

Example 3

Flame pyrolysis of the vapor precursor. This example tests the chemical durability and physical stability of ceramic layers deposited on cordierite honeycombs. FIG. 19 is a flame pyrolysis process stream for this embodimentA flow chart. The ceramic precursor for the synthesis of mullite is: aluminium chloride (AlCl) in solid form ₃ ) And silicon tetrachloride (SiCl) in liquid form ₄ ). Nitrogen (N) ₂ ) As AlCl ₃ Carrier gas of (2.0L/min), and SiCl ₄ Carrier gas (0.3L/min). Solid AlCl ₃ And its carrier gas is passed through a heated sublimator (165 deg.C) for the formation of gaseous AlCl ₃ . Liquid SiCl ₄ And its carrier gas is used to form gaseous SiCl by passing it through a heated bubbler (35 deg.C) ₄ . The target Al/Si mass ratio ranges from 2.9 to 3.8. All heating vessels and pipes were monitored and insulated by T-type thermocouples. The T-type thermocouple is accurate in the temperature range of-270 to 400 ℃, with high sensitivity. All gas flows manage flow accuracy through calibrated Mass Flow Controllers (MFCs). During long run (14-21.5 hours), process control of the Al/Si mass ratio in the range of 2.9 to 3.8A was achieved, as well as stable mullite composition formation.

Containing gaseous AlCl to be carried in heated nitrogen ₃ And SiCl ₄ Is transported to the burner. The inside of the burner has 4 functional gas lines. A premixed methane/oxygen flame having an optimal ratio of 1.25 provides a reaction zone for combustion of the layer precursors. Using internal shielding O ₂ Gas (190 ℃ and 2.0L/min) lifted the combustion zone and forced the just formed particles out of the flame to keep the reaction zone clean. Make up O ₂ The gas (1.5L/min) provides excess oxygen to complete the combustion reaction and to assist in stabilizing the flame. If necessary, additional O may be supplied ₂ Gas (up to 8L/min). The central conduit allows passage of the layer precursor into the flame to produce particles. The 4 different channels can cooperate with each other to provide good flexibility in controlling the flame. Typically, all components of the ceramic precursor vaporization apparatus (e.g., vessels and piping) and burners are insulated and preheated to above 120-190 ℃ to avoid vapor condensation and channel blockage. By controlling the heating temperature and carrier gas flow rate, the composition of the final product is controlled. The burner may be operated in the range of about 175 ℃ to 190 ℃ to help avoid condensation of the central tube and/or due to excessive thermal conductanceResulting in breakage of the seal.

In the burner, the layer precursor is exposed to passage of methane (CH) ₄ ) (5.0L/min) and oxygen (O) ₂ ) (4.0L/min) flame formed by the mixture due to CH ₄ This provides a high temperature reaction zone and a humid environment. Once layer precursor and H ₂ The O is contacted in the flame, the chlorine hydrolyzes and the oxide particles form layer precursors leading to decomposition. The strong collisions between primary particles result in coagulation and coalescence at high temperatures. Some of them grow as large particles, many of them sinter together to form aggregates (agglomerates), and the remaining particles rely on physical bonding to become aggregates (agglomerates). Due to the steep temperature gradient and the high gas flow rate of the flame, all particles and particle groups escape from the flame within milliseconds. It is to be noted that the product morphology (in particular the particle size) may be passed through another heated N ₂ The presence of the gas serves to further dilute the ceramic precursor vapor prior to entering the flame.

The as-formed particles of the decomposed layer precursor were deposited onto stainless steel mesh (316L, 2000DPSI) and ceramic coupons (cut from GPF honeycombs) that were placed on a cylinder mounted above the flame. For filtration efficiency and pressure drop analysis, the as-formed particles were deposited onto full-size ceramic honeycombs (GC 4.055 "-200/8) in wind tunnels used to enhance deposition uniformity and collection efficiency. All deposition processes are assisted by the use of vacuum pumps.

Once the deposition of the particles of the decomposed layer precursors onto the structure (e.g., stainless steel mesh, ceramic coupon, or full-size ceramic honeycomb) is complete, the structure is sintered in an oven set at 1150 ℃ for 30 minutes. After sintering, a crystalline phase ceramic layer is formed.

Fig. 13A and 13B are scanning electron microscope images at different magnifications of amorphous phase decomposed layer precursors deposited onto honeycomb bodies. The as-deposited decomposed layer precursor is porous and all particles are loosely packed to form a continuous structure. Fig. 13C and 13D are scanning electron microscope images at different magnifications of crystalline phase ceramic layers formed after sintering of amorphous phase decomposed layer precursors. The heat treatment causes a change in layer morphology that translates into a well-connected structure, with the particles growing from about 20-40nm (FIGS. 13A-B) to about 60-80nm (FIGS. 13C-D).

Figure 14 shows XRD scans of decomposed layer precursors in as-deposited state, after exposure to 850 ℃ for 6 hours, after exposure to 850 ℃ for 12 hours, and after sintering at 1150 ℃ for 0.5 hours. The as-deposited layer is amorphous, while the main peak of the 1150 ℃ sintered layer corresponds to the mullite standard pattern. The as-deposited particles cannot crystallize at low temperatures (e.g., 850 ℃) even for up to 12 hours. The behaviour of particles based on vapour precursors when crystallised is similar to that of the case where liquid precursors are used, although there is a significant difference in their initial particle size.

The particle size was studied using the BET technique. The results are shown in Table 7.

TABLE 7

In Table 7, the surface area of the as-deposited particles was 61.1m ² A/g which after sintering at 1150 ℃ falls to 47.6m ² (iv) g. The particle size slightly changes when sintered at 850 ℃. The results were consistent with XRD scans. The sintering process is effective for introducing crystalline phases, improving structural integrity, without significantly sacrificing porosity of the mullite layer. The above results show that for the preparation of mullite, the vapor precursor process can achieve the same results as the liquid precursor, including composition, sintered particle size, and even sintered inorganic layer morphology.

The filtration efficiency of a Gasoline Particulate Filter (GPF) was analyzed by depositing the synthetic mullite of this example onto a full size GPF (GC 4.055 "-200/8). Particle filtration test using a simulated Engine (120 Nm particle size, 21 Nm) ³ Flow rate) was used to evaluate filtration efficiency while a clean back pressure test was used to determine pressure drop loss.

Fig. 15 is a representative graph of Filtration Efficiency (FE) versus soot loading and illustrates the increased filtration efficiency by the addition of inorganic layers to a honeycomb body according to embodiments disclosed and described herein. In fig. 15, comparative example 3 is a honeycomb without inorganic layers, and example 3 is a mullite layer of this example. The initial FE of example 3 was increased. Comparative example 3 achieved 97.4% FE for a soot load of 0.01 g/L. Conversely, example 3 can reach 100% FE with significantly lower soot accumulation.

Table 8 is the sample evaluation of example 3.

TABLE 8

According to table 8, the inorganic layer of mullite provides high filtration efficiency (greater than 97%) and low pressure drop loss (only about 5.7%). The number of particles passing through the layer was 5 x 10 ¹⁰ #/Km, and the soot load dP @2g/L is-5.4%. In addition to performance, the strength and durability of the inorganic layer is also relevant for Gasoline Particulate Filter (GPF) applications. The thermal stability of the layer was confirmed by thermal shock, operating window and hydrothermal tests, while the mechanical integrity tests included vibration and high flow in table 8. Thus, with the addition of layers, the existing properties of the starting honeycomb remain unchanged (or change negligibly). The Filtration Efficiency (FE) was little to no degraded for the composite honeycomb and inorganic layers after thermal and mechanical reliability testing.

Fig. 16A and 16B graphically show the back pressure of example 3 and comparative example 3. FIG. 16A is back pressure (kPa) versus flow rate (Nm) of example 3 and comparative example 3 ³ H) graph of the relationship. For example 3, the initial FE of the membrane sample was up to 90.1% (fig. 15), and the DP damage according to fig. 16A was only 5.7%, which is much lower than conventional dip-coated filters. In FIG. 16B, the backpressure rises as the soot loading increases. Example 3 exhibited a lower pressure drop penalty than comparative example 3 when the soot load was higher than 0.5 g/L. This may be interpreted as the layer providing a "on-wall" coating pattern for the filter rather than the "in-wall" situation present in common components.

According to the following testsThe filtration efficiency of the particulate filter manufactured in example 3 was varied. The particulate filter of example 3 was exposed to 850Nm at room temperature ³ High flow conditions of air/h were continued for 1 minute. The filtration efficiency change is determined by measuring the amount of soot particles introduced into the particulate filter and the amount of soot particles exiting the particulate filter before and after exposure to high flow conditions. The soot particles are particles from cigarette smoke having a median particle size of 300nm and being located in an air stream, the soot particle concentration being 500,000 particles/cm ³ At 51Nm ³ Flow rate/h, room temperature and flow rate of 1.7m/s were flowed through the particle filter of example 3 for 1 minute. Filtration efficiency was determined by measuring particle counts using a 0.1CFM lighthouse hand held 3016 particle counter from lighthouse global solutions, inc. Measurements were performed on the particulate filter of example 3 as manufactured, and then exposed to 850Nm at room temperature ³ The measurements were carried out after high flow conditions of/h for 1 minute. Exposure to 850Nm at room temperature ³ The particulate filter of example 3 exhibited a filtration efficiency change of less than 1% after high flow conditions of air/h for 1 minute. This result indicates that the filter material deposits exhibit excellent durability because the filter material deposits remain in place and continue to be effective in providing enhanced filtration efficiency to the particulate filter.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the present description cover the modifications and variations of the various embodiments described herein provided they come within the scope of the appended claims and their equivalents.

Claims

1. A particulate filter, comprising:

wherein one or more of the porous wall surfaces defining the inlet channels comprise a bottom wall portion and a filter material deposit disposed on and chemically bonded to the bottom wall portion, wherein the filter material deposit forms a porous layer comprising a crystalline phase comprising silica and alumina, which is formed from a sintered amorphous phase, and

wherein, the exposure to room temperature is 850Nm ³ The particulate filter exhibits a filtration efficiency variation of less than 5% after a high flow condition of air for 1 minute, and wherein the filtration efficiency variation is determined by measuring the difference between the number of soot particles introduced into the particulate filter and the number of soot particles leaving the particulate filter before and after exposure to the high flow condition, wherein the soot particles have a median particle size of 300nm, the soot particle concentration measured by a particle counter in an air stream flowing through the particulate filter at room temperature and a velocity of 1.7m/s being 500,000 particles/cm ³ 。

2. The particulate filter of claim 1, wherein one or more of the porous wall surfaces defining the inlet channels comprises a bottom wall portion comprising a first ceramic composition, and the deposit of filter material disposed on the bottom wall portion comprises a second ceramic composition, and the first and second ceramic compositions are different.

3. The particulate filter of claim 1, wherein the average thickness of the deposits of filter material is greater than or equal to 0.5 μm and less than or equal to 30 μm.

4. The particulate filter of claim 2, wherein the second ceramic composition comprises alumina or silica, or a combination thereof.

5. The particulate filter of claim 2, wherein the second ceramic composition is selected from the group consisting of: caO, ca (OH) ₂ 、CaCO ₃ 、MgO、Mg(OH) ₂ 、MgCO ₃ 、SiO ₂ 、Al ₂ O ₃ 、Al(OH) ₃ Calcium aluminate, magnesium aluminate, and mixtures thereof.

6. The particulate filter of claim 2, wherein the first ceramic composition is cordierite and the second ceramic composition is alumina.

7. The particulate filter of claim 1, wherein the deposit of filter material comprises an oxide ceramic or an aluminum silicate.

8. The particulate filter of claim 1, wherein the deposit of filter material covers at least 70% of the surface of the porous walls.

9. The particulate filter of claim 1, wherein the deposit of filter material covers at least 90% of the surface of the porous walls.

10. The particulate filter of claim 1, wherein the deposit of filter material extends at least 60% of the distance between the inlet end and the outlet end.

11. The particulate filter of claim 1, wherein the porous ceramic honeycomb structure has a porosity of greater than or equal to 50% to less than or equal to 70%.

12. The particulate filter of claim 1, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 10 μ ι η.

13. The particulate filter of claim 1, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 15 μ ι η.

14. The particulate filter of claim 1, wherein the porous ceramic honeycomb structure has a bulk median pore size of greater than or equal to 8 μ ι η to less than or equal to 25 μ ι η.

15. The particulate filter of claim 1, wherein 850Nm exposure to room temperature ³ The particulate filter exhibits a filtration efficiency variation of less than 3% after 1 minute of high flow conditions of air, and wherein the filtration efficiency variation is determined by measuring the difference between the number of soot particles introduced into the particulate filter and the number of soot particles leaving the particulate filter before and after exposure to the high flow conditions, wherein the soot particles have a median particle size of 300nm, the soot particle concentration measured by a particle counter in an air stream flowing through the particulate filter at room temperature and a velocity of 1.7m/s being 500,000 particles/cm ³ 。

16. The particulate filter of claim 1, wherein the deposit of filter material comprises synthetic mullite.

17. The particulate filter of claim 1, wherein the deposits of filter material are disposed on the bottom wall portion to provide the deposits of filter material with a porosity greater than 90%.